FLUID MACHINE, AND REFRIGERANT CIRCUIT AND WASTE HEAT UTILIZATION DEVICE USING THE FLUID MACHINE

[Purpose] To provide a fluid machine, and a refrigerant circuit and a waste heat utilization device using the fluid machine, whereby the size and cost of a Rankine circuit and thus of the waste heat utilization device can be reduced while preventing an abnormally high pressure from being developed in the Rankine circuit and also improving starting performance of the Rankine circuit. [Means for Attaining the Purpose] A waste heat utilization device (1) is provided with a Rankine circuit (4) including a fluid machine (10). The fluid machine (10) includes, inside a housing thereof, a drive section (22) configured to be driven by a working fluid introduced from an inlet port (33) and to discharge the working fluid to an outlet port (45), a communication passage (102) allowing the working fluid to flow from the inlet port into the drive section, a bypass passage (104) allowing the working fluid to flow from the inlet port to the outlet port while bypassing the drive section, and a valve mechanism (106, 112, 124) configured to block inflow of the working fluid from the inlet port and to allow the inlet port to be connected selectively to the communication passage and the bypass passage.