The refrigerant leakage determination device includes a refrigerant detection sensor that detects presence of gas and transmits a concentration of the gas as a sensor output, an alarm device that issues an alarm about leakage of refrigerant, and a controller configured to control the alarm device based on the sensor output from the refrigerant detection sensor. The controller includes a storage device that stores two thresholds for the sensor output and two set times each having a length set for each threshold, and a processing device that, when the sensor output exceeds one or both of the two thresholds and a length of a time period during which the sensor output exceeds the one or both of the two thresholds is longer than either one of the two set times associated with the two thresholds, determines leakage of refrigerant and actuates the alarm device.