The Japanese labor law limits working hours of regular employees but the restrictions do not apply to workers in supervisory positions.
The worker was on loan to another Mitsubishi Electric unit from April 2013 and became mentally ill after working extensively at a plant in Toyooka in Hyogo Prefecture.
It rewards workers based on fixed overtime work hours instead of actual hours worked.
We will work on thoroughly implementing appropriate labor control," Mitsubishi Electric said in a statement Friday.
The labor authorities awarded workers' compensation to five employees at Mitsubishi Electric between 2014 and 2017, of whom two had committed suicide.