Tony Hogg, who was elected in November 2012, made the announcement on his website and said he was "proud of his achievements".
For the remaining eight months, he said his priorities included improving police funding for the force.
PCCs work to ensure police forces are running effectively and replaced police authorities.
The government insists they are not there to run local police forces but to hold them to account and respond to the needs of the public.
Mr Hogg told the BBC he would still be doing the job in his 70s if he was re-elected and he wanted to spend more time with his family.
It is a very big job and Tony Hogg has had a tough time with many members of the public being very sceptical over what he would achieve.
He has had to deal with cuts, cuts and more cuts. Since 2011, officer numbers in the force have fallen by about 400.
Looking ahead, he's facing more cuts. From talking to senior officers they expect the number of officers to fall below 3,000, in fact some say it is the minimum number Devon and Cornwall can be policed with and I think Mr Hogg has accepted he will not be able to maintain that number.
It is a very tough time to be a leader in this sector.
Devon and Cornwall's Police and Crime Commissioner (PCC) has announced he will not be seeking re-election in May.