To provide a hydraulic generator with a simple structure preventing a cooler from clogging and breaking down, and improving reliability of a cooling system.

In this hydraulic generator having a hydraulic supply system 3 comprises a reservoir 2, a supply line supplying oil from the reservoir 2 into hydraulic equipment 6, a hydraulic supply pump 5 applying pressure to the oil, a drain line 8 returning the oil from the hydraulic equipment 6 to the reservoir 2, or a vent line 7, a cooler 13 is provided in isolation from the hydraulic supply system 3 wherein a cooling line circulating the oil between the reservoir 2 and the cooler 13 and a circulating pump 10 are arranged.