The minimum prison term has risen from 20 to 40 years.
It will apply for all abductions, including those that last only a few hours or days, so-called "express kidnappings".
The maximum prison sentence will rise from 50 to 140 years for those who kill their victims.
Kidnappings committed by a public security official, such as a member of the police or military, will be punished with up to 100 years in prison.
Kidnappers will also have to pay heavy fines.
In reality, few people ever receive sentences longer than 60 years for federal crimes, but kidnapping is considered in a separate category.
The number of kidnappings reported to the police has risen dramatically in Mexico in recent years.
In 2007, 438 kidnappings were reported, but the number had risen to almost 1,700 last year.
And the government estimates the number of kidnappings reported to the police could be fewer than 2% of the total.
If that is the case, the real number of abductions could be about 105,000 per year.
Analysts say accurate figures are hard to come by, as many abductions only last for hours or a few days until the victims empty their bank accounts at gunpoint or pay a ransom.
Most are never reported to the authorities for fear of reprisals from the criminal gang which carried out the kidnapping.
In January this year the Mexican government launched a nationwide effort to fight kidnapping.
A federal prosecutor, Renato Sales, was named to head an anti-kidnapping committee that would co-ordinate efforts to fight abductions in the 10 Mexican states (out of 31) where 74% of all kidnappings take place.
"Mexico needs to deal quickly and efficiently with the humanitarian emergency that this crime entails," said Mr Sales at the time.

PC Peter Hodgkinson discharged the weapon while Andrew Pimlott, 32, was holding a lit match at his parents' home in Plymouth in April 2013.
Mr Pimlott caught fire and died from his injuries five days later.
The officer said he only fired because he feared Mr Pimlott was about to send himself up in flames.
The inquest heard two police officers went to the home of Mr Pimlott's parents after his father called 999.
His father Kelvin said his son had a can of petrol and was threatening to set fire to the building.
The inquest previously heard the dead man had been served with a restraining order preventing him contacting his parents or going near their home.
After PC Peter Hodgkinson and PC David Beer arrived at the scene, they saw Mr Pimlott, who was in the back garden, douse himself in petrol from a can and strike a match.
"I deployed the Taser to reduce the risk the of harm to Mr Pimlott," said PC Hodgkinson.
"I tried to engage with him to put down the can. I believe he was going to set himself alight so I fired the Taser."
PC Beer said: "I heard the Taser sound being activated and Mr Pimlott went up in flames."
Independent fire investigator Steven Andrews said he made a "very strong finding" that Mr Pimlott was set on fire by the Taser.
The ignition point was on the belly where the Taser hit.
"The evidence does not support that he was set alight by the match," he said.
The inquest continues.

Kirklees Council had been consulting on plans to replace paid staff at seven sites in Huddersfield with volunteers.
Protesters who gathered outside a council meeting on Wednesday said a survey had showed 66% of people were opposed to the plan.
The council later said there would be no changes for three years. Campaigners said the decision was "wonderful".
The changes would have affected libraries at Honley, Golcar, Slaithwaite, Lepton, Kirkheaton, Denby Dale and Shepley.
Campaigner June Jones said replacing professional library staff with volunteers was not sustainable and was likely to have led to library closures.
Ms Jones, of Save Slaithwaite Library, said: "It's wonderful for our communities and we are going to be drinking champagne for the next week."
Mexico has published new sentencing guidelines that will double prison sentences for kidnapping.
[NEXT_CONCEPT]
A police officer said he hoped a shot from a Taser stun gun would prevent a man soaked in petrol setting himself alight, an inquest has heard.
[NEXT_CONCEPT]
Planned cuts to library services in a West Yorkshire town have been scrapped following campaigns by residents.