The working medium for heat cycle, heat cycle system composition and thermodynamic cycle system

Temperature gradient is small, the discharge temperature is sufficiently low, high durability, less impact on global warming, excellent management of the system, and actuating the heat cycle providing heat cycle system excellent in cycle performance (capacity) medium provides compositions and thermodynamic cycle system for a thermal cycling system. Includes trifluoroethylene and difluoromethane, the ratio of the total amount of trifluoroethylene and difluoromethane for working medium for heat cycle the total amount exceeds 90 wt%, represented by trifluoroethylene / the difluoromethane in working medium for heat cycle thermal cycling system using the mass ratio of 41 / 59-59 / 41 for thermal cycling medium and thermal cycle system composition is, and these.