To save energy by simultaneously using a heater and a high pressure refrigerant supplied to an evaporator in deicing operation.

An ice making part 10 has the evaporator 14 and the heater communicating with and connected to a refrigerating circuit 30. The ice making part 10 is cooled by circulating and supplying the vaporized refrigerant to the evaporator 14 in ice making operation, and an ice mass is generated by supplying ice making water to the ice making part 10. In the deicing operation, the ice mass is melted and separated from the ice making part 10, by heating the heater by carrying an electric current, after a predetermined time passes after supplying a gas-liquid mixed refrigerant having relatively high pressure to a refrigerant pipe 34 connected to the delivery side of the evaporator 14 via a bypass circuit 40 of interposing a bypass valve HV.