Electric power generation control system for internal combustion engine

A power generation control system (1) for an internal combustion engine (3), is capable of preventing occurrence of vibration of the engine (3) when the engine (3) is being stopped and improving fuel economy through electric power generation as much as possible. The power generation control system (1) disengages a clutch (7) for a predetermined time period after satisfaction of idle stop conditions, and inhibits electric power generation by a generator (8), to thereby prevent sharp reduction of engine speed. Further, an ISV (13) opening is controlled to a predetermined very small value close to 0. This makes it possible to prevent occurrence of vibration of the engine (3) at an idle stop. Further, when the engine speed becomes not larger than a threshold value, electric power generation is started, whereby it is possible to secure a time period over which electric power generation is executed to improve fuel economy through electric power generation.