8 November 2016 Last updated at 10:40 GMT
It's about 30 metres long and it's thought it may have been caused by work on an underground train line in the city of Fukuoka on the southern Japanese island of Kyushu.
It began with two smaller holes that grew steadily until they formed one huge crater.
Nobody has been hurt by the sinkhole but it has affected power, water, and gas supplies.
People who live and work nearby have been evacuated.
Check out this video.

Albanians Artur Doda, 24, and Leonard Isufaj, 27, leapt from the Stena Britannica, off Harwich, Essex, on 26 February last year.
The pair had tried to enter the UK hours earlier inside a lorry, the inquest into their deaths in Chelmsford heard.
Coroner Eleanor McGann recorded conclusions of accidental death.
Mr Doda and Mr Isufaj were among a group of 15 people from different countries caught in a random x-ray check at Harwich before making it into the UK.
The inquest heard Mr Doda was sliced by the "machete-like" motion of the ship's propeller while Mr Isufaj drowned.
Both men were sucked underwater almost immediately after they jumped over the side of the ship, ten minutes into its journey back to Zeebrugge, Belgium.
Essex coroner Ms McGann said: "The evidence suggests they were intending to swim back to England, something that they could see was tantalisingly close to them."
Insp Christopher Willis, from Essex Police, told the hearing the sea would have appeared deceptively calm to the men.
"To swim to land with those tides and the water temperature would have been nigh-on impossible," he said.
"An Olympic swimmer would have struggled."
Speaking after the hearing, Mr Isufaj's cousin, Besnik Vata, 33, from north London, said the case highlighted the plight of many immigrants.
"We heard that they weren't escorted on board the ship so there was always a risk this would happen - if I was in that position I would have done the same," he said.
Border Agency official Giles Young said there was no policy of escorting deportees in place.

A graphic joking about a murdered sex worker, and another about infecting a partner with a sexually transmitted disease were posted on the attraction's Twitter feed.
Critics said the collection of images was sexist and offensive.
Merlin Entertainment said it was "very sorry" for the campaign and has deleted the tweets.
The group said it had wanted to run a "dark Valentine campaign" to promote the London Dungeon, in which visitors are taken on a tour through London's dark history.
But many Twitter users complained that many of the images tweeted were in poor taste and inappropriate for a family tourist attraction.
Rebecca Reid, a columnist for the Telegraph, said: "The biggest issue here is taking violence against women and turning it into a joke or a cheap marketing ploy."
She told the BBC: "Just because these rapes and murders happened in the past doesn't mean they are fair game.
"Violence, rape and murder are all still a very brutal reality of life for modern day sex workers and these flippant tweets show no awareness or respect for that."
Merlin Entertainment said: "Our brand tone of voice tends to divide audiences. However, we recognise that we've upset some people and for that we're very sorry."
Check out this giant sinkhole in a road in Japan!
[NEXT_CONCEPT]
Two deportees who died after jumping from a ferry were trying to swim back to the UK shore, an inquest has heard.
[NEXT_CONCEPT]
The London Dungeon tourist attraction has apologised for a promotional Twitter campaign that backfired.