A liquid power generation apparatus includes a movable liquid tank, a linear-rotation conversion mechanism, liquid introducing device, controlling device, liquid discharging device, liquid tank returning device, and a generator. The movable liquid tank can vertically move. The linear-rotation conversion mechanism includes a male screw shaft and a female screw body and generates a rotation output in tandem with the vertical movement of the movable liquid tank. The liquid introducing device introduces a liquid when the movable liquid tank is provided at an upper position. The controlling device moves down the movable liquid tank having the liquid therein from the upper position. The liquid discharging device discharges the liquid when the movable liquid tank is lowered. The liquid tank returning device moves up the lowered movable liquid tank and returns it to its original position. The generator generates electricity by using a rotation output from the linear-rotation conversion mechanism.