A working fluid for heat cycle, wherein the global warming potential is less than 300; the product of the relative coefficient of performance and the relative refrigerating capacity is at least 0.820 relative to R410A in a standard refrigerating cycle under conditions of an evaporation temperature of 0° C., a condensing temperature of 40° C., a supercoiling degree of 5° C. and a degree of superheat of 5° C.; the relative compressor discharge gas pressure is at most 1.100; the lower limit of the combustion range by method A in High Pressure Gas Safety Act is at least 5 vol %; and the pressure will not exceed 2.00 MPaG in a combustion test by method A in High Pressure Gas Safety act under 0.98 MPaG at 250° C.