To reduce a burden on a CPU without using a calculation table in electronic governor control of an engine using a central processing unit.

A control variable of a throttle valve for adjusting a fuel supply quantity is calculated so as to eliminate a deviation of an actual engine speed to a target engine speed of the engine. The control variable is calculated by an arithmetic operation part 107 composed of the central processing unit (CPU). A first calculating part 107A calculates a deviation D of a present engine speed to the target engine speed Ne (tgt). The deviation D is corrected by a correction value A on the basis of a difference between the actual engine speed Ne (0) and an engine speed Ne (-1) of the last time and a correction value B on the basis of a difference between an engine speed of the last time and an engine speed Ne (-2) of time before the last time. A second calculating part 107B calculates a correction value E taking into consideration a load by throttle opening θTH (0) and the target engine speed Ne (tgt). A third calculating part 107C calculates D/E, and outputs a throttle opening-closing value PθTH.