Purging device, chiller equipped with same, and method for controlling purging device

A purging device that includes a purging pipe for purging a gas mixture containing a coolant and a non-condensable gas from a chiller; a purging tank; a cooling device that has a cooling heat-transfer surface provided therein which condenses the coolant in the gas mixture and is oriented in the height direction inside the purging tank; a drainage pipe for discharging the liquid coolant inside the purging tank to the chiller; an exhaust; a purging tank pressure sensor for measuring the pressure inside the purging tank; and a control device which detects that an increase in the level of the liquid coolant inside the purging tank has occurred when the measured value from the purging tank pressure sensor decreases, and thereafter, increases to a prescribed value or higher, when condensing the coolant by cooling the interior of the purging tank using the cooling device.