A cooling box to control temperature so that an internal temperature of the cooling box becomes equal to a set temperature, includes: a control device including an temperature sensor to detect an ambient temperature of the box, and adjust a supply amount of warm air into the box after stopping supply of cold air thereinto based on the ambient temperature; and a door sensor to detect whether an opening connected with the interior of the cooling box is in either an open or closed state, when the door sensor detects a change of the opening from an open to closed state. The control device executes control so that the warm-air-supply-amount reaches a first value until a predetermined period has elapsed, and executes control so that the warm-air-supply-amount reaches a second value smaller than the first value after the predetermined period has elapsed.