A gradient magnetic field coil unit includes a main coil layer that has a main coil for generating a gradient magnetic field and is formed in a substantially cylindrical shape. A shield coil layer that is attached to the outside of the main coil layer and has a shield coil for generating a magnetic field which shields a leakage magnetic field from the main coil. A cooling layer is attached between the main coil layer and the shield coil layer and has a plurality of flow paths for refrigerant. The flow paths are arranged in a substantially circumferential shape with the central axis of the main coil layer set to the center thereof, and a plurality of shim tray holding sections which hold a shim tray for a magnetic body.