Abstract: A structure for controlling an engine is simplified in a power generation device equipped on a vehicle which generates power by a driving force of an engine. An operation unit (32) outputs to a controller (12) drive operation information based on an operation of a user. The controller (12) controls a vehicle driving circuit (28) and determines an engine output power target value based on the drive operation information and a running state of the vehicle. An engine output power/control voltage table stored in a storage unit (34) is referred to, and a value of a control voltage (Va) correlated to the engine output power target value is determined. The controller (12) controls a voltage adjusting circuit (24) such that the control voltage (Va) is set to the value determined based on the engine output power/control voltage table.