A power generator includes a heavy gyro body, a driving device, a transmission disk and an electricity generation module. The driving device is used to drive the heavy gyro body to rotate about a vertical spindle. The transmission disk is secured to and rotatable simultaneously with the heavy gyro body. The transmission disk has a plurality of rollers at a sidewall thereof. The electricity generation module has a rotation disk, which has a plurality of inclined grooves at a sidewall thereof. Each inclined groove is meshed with a corresponding roller of the transmission disk such that the transmission disk is able to drive the rotation disk to rotate, wherein an included angle between an inner sidewall of each inclined groove and a horizontal plane is more than 0 degree and less than 45 degrees.