A cold accumulation type refrigerating machine having a high refrigeration efficiency. Rotation output of a stepping motor is converted to a reciprocative motion of a displacement member carrying a cold accumulator and disposed within a cylinder in which first and second closed chambers are defined above and below the displacement member, respectively. A compressed gas discharged from a compressor is introduced into the second closed chamber through the cold accumulator upon opening of a suction valve and undergoes expansion within the second closed chamber, the gas being then fed back to the compressor through the cold accumulator upon opening of an discharge valve, whereupon one cycle of refrigerating operation is completed. Rotation speed of the stepping motor is varied during every one cycle of operation by means of a pulse oscillation controller such that a time taken for the displacement member to reach a top dead center position from a time point at which the discharge valve is opened is increased while the remaining period of the one cycle is correspondingly shortened.
