To shorten defrosting time and to improve operation efficiency by a method wherein a flow passage is switched after the pressures of refrigerants in a low pressure output port, a high pressure input port, a through-hole communicating with an indoor heat-exchanger, and a through-hole communicating with an outdoor heat-exchanger are uniformized with each other by a four-way valve.

A communication groove 21 through which an output port 11 communicating with the refrigerant suction port of a compressor 40 during cooling operation communicates with a through-hole 23 communicating with an indoor heat-exchanger 41 is formed in an under surface 8b of a main valve body 8. Further, a guide groove 22 through which an output port 12 communicating with the refrigerant delivery port of the compressor 40 communicates with a through-hole 24 communicating with an outdoor heat-exchanger 42 is formed. Simultaneously with conduction between the output port 11 and a through-hole 23, conduction between an input port 12 and the through-hole 24 is effected and simultaneously with conduction between the output port 11 and the through-hole 24, conduction between an output port 12 and the through-hole 23 is performed. The pressures of the refrigerant suction port and the refrigerant delivery port of the compressor 40 are uniformized with each other. This constitution improves the operation efficiency of a refrigerant cycle through reduction of a defrosting time and reduces a consumption power.