Provided is a power steering apparatus capable of suppressing an abrupt change in steering force and preventing a deterioration in steering feeling even in the event of a transition from power steering to manual steering. The power steering apparatus includes a torque sensor, a motor of a permanent magnet field type, and a controller having a motor driving unit and an abnormality monitoring unit, for controlling the driving of the motor. The motor driving unit includes an inverter for driving the motor, and a drive signal generating unit for calculating a target current caused to flow through the motor and outputting a drive signal of the inverter based on the target current. The abnormality monitoring unit includes an abnormality processing unit for constituting a closed-loop circuit including the motor in stopping the driving of the motor.