A four-way switching valve free from leakage of a refrigerant. A pressure-regulating chamber is switchably connected to a low-pressure chamber or a high-pressure chamber by a three-way solenoid valve, and a pressure-regulating chamber is communicated with a chamber by a tube. When the three-way solenoid valve connects the pressure-regulating chamber to the low-pressure chamber, a plug is urged by the high pressure, thereby permitting port A and a port B to communicate with each other, while inhibiting the port B and a port D from communicating with each other. The pressure within the chamber is increased to thereby increase the pressure within the pressure-regulating chamber. Consequently, a plug is urged by a piston to thereby inhibit the port A and a port C from communicating with each other, and permitting the port C and the port D to communicate with each other. Inversely, when the three-way solenoid valve connects the pressure-regulating chamber to the high-pressure chamber, the plug is urged by a piston to thereby inhibit the port A and the port B from communicating with each other, and permitting the port B and the port D to communicate with each other. The pressure within the chamber is reduced to thereby reduce the pressure within the pressure-regulating chamber. Consequently, the plug is urged by the high pressure to thereby permitting the port A and the port C to communicate with each other, while inhibiting the port C and the port D from communicating with each other. This makes it unnecessary to cause leakage of the refrigerant to reduce pressures within the pressure-regulating chambers.