To provide a power steering unit which allows smooth operation of a first spool valve of a control valve and facilitates processing and assembling.

A first spool valve 28 is provided which defines the inside of a spool valve accommodation hole 25 of a control valve 20 into a first oil chamber 29 for communicating to a power cylinder, a second oil chamber 30 for communicating to a drain passage, and a third oil chamber 31 for communicating to a supply passage 47. A second spool valve 37 is provided which is operated with an operation force in accordance with the steering torque and pressurized to the side of the first spool valve 28 by the hydraulic pressure of the power cylinder. A communication passage 36 is provided for communicating the first oil chamber 29 to the second oil chamber 30. A supply spring 42 is provided for energize the first spool valve 28 to the side of the second oil chamber 30. Hydraulic oil is guided from the supply passage 47 to the first oil chamber 29, via the third oil chamber 31, by moving through the second spool valve 37 and the first spool valve 28. Therefore the hydraulic oil can be supplied to the power cylinder.