The invention provides a control device and a control method of a refrigerated storage. In-storage temperature constant control is carried out via PID control during constant-temperature cooling so as to keep the in-storage temperature to be constant; growth of frost in an evaporator is obstructed; frequency to carry out defrosting can be reduced; and period time of defrosting is extended. A heat supplying procedure and a heat cutting off procedure are alternatively repeatedly carried in the in-storage temperature constancy control. In the heat supplying procedure, regulated heat supplying time when an expansion valve is opened is regarded as a heat supply state and regulated heat cutting off time when the expansion valve is closed is regarded as a heat cutting off state.