PURPOSE: To prevent a compressor from being abnormarily interrupted owing to excessive lowering of low pressure by providing pump down starting control means which closes a liquid pipe opening/closing valve when a detected value by low pressure detector means is higher than a set value upon starting the compressor to start the compressor.

CONSTITUTION: There are provided a liquid pipe opening/closing valve disposed in the course of a liquid pipe located from a condenser 2 of a refrigerant circuit to a pressure reducing valve 4, and low pressure detector means LPT for detecting low pressure in a refrigerant circuit A. When a detected value by low pressure detector means LPT is higher than a set value upon starting a compressor 1, pump down starting control means 101 starts the compressor 1 in the state where the liquid pipe opening/closing valve LSV is closed, while the amount of circulation of the refrigerant is reduced owing to pump-down action and hence low pressure is lowered. Accordingly, a time interval a stable state is attained after the starting of the compressor 1 can be shortened and hence the compressor 1 is prevented from being badly started.