PURPOSE: To cause a predetermined cold heat amount to be easily accumulated irrespective of some causes of external disturbance by a method wherein there are provided means for sensing a heating degree index of refrigerant passed through an evaporator during a cold heat accumulation and means for discriminating a cold heat amount accumulated in a cold heat accumulation tank in response to a detected information.

CONSTITUTION: When a cold heat amount accumulated in a cold heat accumulation tank 3 is increased under a cold heat accumulation mode, cold heat generated at an evaporator 4 is hardly removed by a latent cold heat accumulation material 5, resulting in that a calculated over-heating degree S is reduced. Then, although an super-heating degree control part 12 increases a super-heating degree, the super-heating degree is apt to be reduced as the cold heat amount is increased, resulting in that the number of rotation of a compressor CMP is decreased and the detected number of rotation KN sensed by the number-of-rotation sensor 10 becomes a super-heating degree index indicating a reduced super-heating degree of refrigerant. In addition, a discriminating part 17 of the cold heat amount control part 13 judges that a predetermined cold heat amount is accumulated in the cold heat accumulation tank 3 as the detected number of rotation KN is decreased lower than a set number SN, and an operation stopping signal output part 18 outputs an operation stop signal to an output adjusting part 16 so as to stop the operation under a cold heat accumulation mode.