PROBLEM TO BE SOLVED: To provide a gradient magnetic field power supply capable of suppressing occurrence of dew condensation in hot and humid conditions.SOLUTION: A gradient magnetic field power supply includes an output amplifier, a heat exchanger 44, a piping pipe 48 and a valve. The output amplifier amplifies electric current and outputs the amplified electric current to a gradient magnetic field coil. The heat exchanger exchanges heat between the air in an enclosure provided with the output amplifier, and a cooling medium. The piping pipe supplies the cooling medium to an object to be cooled including the heat exchanger and the output amplifier. The valve is mounted on the piping pipe to supply the cooling medium to the object to be cooled under the condition for preventing occurrence of dew condensation on the object to be cooled including at least the output amplifier other than the heat exchanger.
