A power steering device includes an oil-hydraulic pump, an electric motor to drive the pump, an inverter, a control valve, a power cylinder to produce a steering assist, and a control unit to control the drive signal of the inverter. The control valve includes a pump port supplied with oil from the pump, a first and second cylinder ports connected to first and second cylinder chambers on sides of the piston, and a discharge port. Communication between the first cylinder port and the pump port and communication between the second cylinder port and the discharge port, and communication between the first cylinder port and the discharge port and communication between the second cylinder port and the pump port are established in steered status in the other direction. Communication among the pump port and first and second cylinder ports, and isolation of the discharge port from the pump port and first and second cylinder ports are established when the control valve is in neutral status.