Provided is a control circuit capable of efficiently supplying electric power from an alternating-current generator to a load, and a power generation device having this control circuit. A control circuit 1 for controlling electric power to be supplied from a power generator 5 to a battery 6 is provided with: a rate-of-change obtaining unit 11 configured to obtain a rate of change of a sensor cycle for a sensor signal synchronous with an operation of the power generator 5; an estimation unit 12 configured to estimate a next sensor cycle using the rate of change of the sensor cycle obtained by the rate-of-change obtaining unit; and an output-supply control unit 13 configured to perform PWM control of switching elements provided for a drive circuit 30 using the next sensor cycle estimated by the estimation unit 12.