To obtain a high output though forming in compactness, in a hydraulic unit including a hydraulic pump driven to rotate in a single direction of rotation.

A hydraulic unit is applied to a power steering device A mounted in a vehicle. In one end 11 of a rotary shaft 10 of a hydraulic pump 7, a first gear member 36 is provided able to integrally rotate, the first gear member 36 is connected through one-way clutch 15 to an output shaft 23 connected to an engine. A second gear member 37 meshed with the first gear member 36 is connected through a second one-way clutch 16 to a rotary shaft 17 of an electric motor 14. At low speed running time, the oil hydraulic pump 7 is driven by only the electric motor 14, and at high speed running time, the oil hydraulic pump 7 is driven by only the engine 13.