There is provided a working fluid for heat cycle that uses (Z)-1-chloro-2,3,3,3-tetrafluoropropane (HCFO-1224yd(Z)) which has a less impact on the ozone layer, has a less impact on global warming, and has excellent cycle performance, the working fluid for heat cycle having sufficiently ensured stability and having high productivity. The working fluid for heat cycle contains HCFO-1224yd(Z) and an impurity, wherein the impurity includes a specific trace component, and a total content ratio of the trace component to a total amount of the working fluid is less than 1.5 mass %.