To simultaneously achieve both of size-reduction of the entire apparatus and enhancement of power generation efficiency, especially by employing double power generation by the lower part and the upper part.

A hydraulic power generating apparatus includes: a conveyance chain 19 that annularly runs between a pair of upper gear 15 and a lower gear 16 provided up and down; double generators connected to rotary shafts of the gears and driven by an upper part and a lower part depending on the rotation of respective gears; a plurality of containers 13 provided to the conveyance chain at predetermined intervals so as to make a bottom surface toward the circulation movement direction thereof; a water supply means 12 for supplying water from the above with respect to the containers 13a at the predetermined positions at the upper part; and a water supply pipe 14 for supplying water from the side. The conveyance chain moves and circulates between the upper gear and the lower gear based on gravity of water supplied to the containers by the water supply means, and thereby rotates the upper gears, thus performing double power generation by the upper part and the lower part.