The man, in his 40s, had been driving ambulances and fire trucks for more than 20 years.
The case came to light when the firefighter hesitated to show his license during a routine inspection. When the inspector took the driver's license and checked closely, it belonged to his family member.
"An inspector thought he was looking awkward and yanked the driver's license from his hand and discovered it was his father's," said Sawasaki, a Takaoka City official.
The firefighter, whose name the city official declined to announce, had been using his father's license and showing it to the inspector while hiding the photograph with his fingers.
Between April 2003 and June 2008, the man drove ambulances 309 times and fire trucks 97 times without accidents.
The firefighter is at present being questioned by the police.
