An incubator comprising: an enclosure including a culture chamber whose temperature is controlled depending on a set temperature; a heater configured to heat the culture chamber; a refrigerator including an evaporator configured to evaporate a cooling medium to allow the cooling medium to absorb heat from the culture chamber and a condenser configured to allow the cooling medium to release heat to condense the cooling medium, the refrigerator configured to cool the culture chamber; a temperature sensor configured to measure the temperature of the culture chamber; a refrigerator control unit; a heater control unit configured to control the heater in such a manner that the measured temperature reaches a temperature for refrigerator-operation, when operation of the refrigerator is stopped, characterised in that the refrigerator control unit is programmed to cause the refrigerator to operate, when a measured temperature measured by the temperature sensor reaches the temperature for refrigerator-operation, which is higher than the set temperature by a first temperature (TrH), and cause the refrigerator to stop operating, when the measured temperature reaches a temperature for stopping refrigerator-operation, which is lower than the set temperature by a second temperature (TrL); the incubator further comprises a drain mechanism configured to discharge dew condensation water generated through heat absorption by the evaporator out of the enclosure, and the heater control unit is programmed to switch between a first mode and a second mode in accordance with a selection signal selected by an operator, wherein the first mode is a mode where the heater is controlled in such a manner that the measured temperature matches the set temperature, and the second mode is a mode where the heater is controlled to generate heat greater in amount than heat in the first mode in such a manner that the measured temperature reaches the temperature for refrigerator-operation when operation of the refrigerator is stopped. an enclosure including a culture chamber whose temperature is controlled depending on a set temperature; a heater configured to heat the culture chamber; a refrigerator including an evaporator configured to evaporate a cooling medium to allow the cooling medium to absorb heat from the culture chamber and a condenser configured to allow the cooling medium to release heat to condense the cooling medium, the refrigerator configured to cool the culture chamber; a temperature sensor configured to measure the temperature of the culture chamber; a refrigerator control unit; a heater control unit configured to control the heater in such a manner that the measured temperature reaches a temperature for refrigerator-operation, when operation of the refrigerator is stopped, characterised in that the refrigerator control unit is programmed to cause the refrigerator to operate, when a measured temperature measured by the temperature sensor reaches the temperature for refrigerator-operation, which is higher than the set temperature by a first temperature (TrH), and cause the refrigerator to stop operating, when the measured temperature reaches a temperature for stopping refrigerator-operation, which is lower than the set temperature by a second temperature (TrL); cause the refrigerator to operate, when a measured temperature measured by the temperature sensor reaches the temperature for refrigerator-operation, which is higher than the set temperature by a first temperature (TrH), and cause the refrigerator to stop operating, when the measured temperature reaches a temperature for stopping refrigerator-operation, which is lower than the set temperature by a second temperature (TrL); the incubator further comprises a drain mechanism configured to discharge dew condensation water generated through heat absorption by the evaporator out of the enclosure, and the heater control unit is programmed to switch between a first mode and a second mode in accordance with a selection signal selected by an operator, wherein the first mode is a mode where the heater is controlled in such a manner that the measured temperature matches the set temperature, and the second mode is a mode where the heater is controlled to generate heat greater in amount than heat in the first mode in such a manner that the measured temperature reaches the temperature for refrigerator-operation when operation of the refrigerator is stopped. the first mode is a mode where the heater is controlled in such a manner that the measured temperature matches the set temperature, and the second mode is a mode where the heater is controlled to generate heat greater in amount than heat in the first mode in such a manner that the measured temperature reaches the temperature for refrigerator-operation when operation of the refrigerator is stopped.