To provide a method and a device for driving power steering for a ship to suppress an engine output loss by steering a ship with a necessary and sufficient hydraulic drive force by a hydraulic cylinder, highly efficiently driving the hydraulic cylinder by eliminating a waste of pressure, with improved mountability on a ship by simplifying structure.

A power steering device of a ship is provided with a handle 10 coupled to a ship to be steered through a wire 11 and the hydraulic cylinder 14 for steering aids, and a hydraulic pump 15 to drive the hydraulic cylinder 14. Further, the power steering device for a ship is provided with a steering force detecting means 17 to detect a steering force by operation of a handle, an electric motor 16 to drive the hydraulic pump 15, and a controller 23 to drive a control the electric motor according to a steering force detected by the steering force detecting means 17.