Abstract: An apparatus for detecting refrigerant leak in a refrigerating apparatus using refrigerant and a heat pump type refrigerating apparatus at low cost is presented. A refrigerant leak is judged from the differential temperature and the running time, by comprising a refrigeration system including a compressor, an evaporator, an expansion device, and a condenser, being sequentially coupled annularly by a conduit, a first temperature detector for detecting the air temperature of suction port of the evaporator, a second temperature detector for detecting the refrigerant temperature at the middle part of the evaporator, a differential temperature detector for calculating the differential temperature of the detectors, and a running time detector for storing the cumulative running time of the compressor.