An anomaly detector configured to be add to an environmental tester including a thermostat-humidistat container including a test chamber, a heating device for heating the test chamber at an amount of heating corresponding to an amount of electric power supplied to the heating device, a humidifying device for humidifying the test chamber at a humidification amount corresponding to an amount of electric power supplied to the humidifying device, and a refrigeration apparatus in which a refrigerant is circulated to cool the test chamber by a refrigeration cycle, the anomaly detector comprising: a controlling section configured to receive a heating electric power value representing the amount of electric power supplied to the heating device and a humidifying electric power value representing the amount of electric power supplied to the humidifying device, wherein the controlling section compares the heating electric power value and the humidifying electric power value with predetermined reference electric power values of the heating device and the humidifying device, respectively, and when at least one of the heating electric power value or the humidifying electric power value is less than a corresponding one of the reference electric power values, the controlling section makes a determination that a cooling capacity of the refrigeration apparatus has been reduced, and outputs an anomaly signal indicating the determination, wherein the controlling section includes a receiver configured to receive determined temperature and humidity values representing a temperature and a humidity determined in the test chamber, set temperature and humidity values representing a preset temperature and a preset humidity of the test chamber, the heating electric power value, and the humidifying electric power value, a stability determining section configured to determine that the temperature and the humidity in the test chamber are in a stable state when the determined temperature and humidity values keep matching the set temperature and humidity values, respectively, for a predetermined period of time, a data memory configured to store stable electric power values of the heating device and the humidifying device in the stable state when the stability determining section determines that the temperature and the humidity in the test chamber are in the stable state, and a comparison and determination section configured to compare the heating electric power value and the humidifying electric power value with predetermined reference electric power values of the heating device and the humidifying device, respectively for the determination, and output the anomaly signal, wherein each of the reference electric power values is obtained by multiplying a corresponding one of the stable electric power values stored in the data memory by a predetermined anomaly detection coefficient. a controlling section configured to receive a heating electric power value representing the amount of electric power supplied to the heating device and a humidifying electric power value representing the amount of electric power supplied to the humidifying device, wherein the controlling section compares the heating electric power value and the humidifying electric power value with predetermined reference electric power values of the heating device and the humidifying device, respectively, and when at least one of the heating electric power value or the humidifying electric power value is less than a corresponding one of the reference electric power values, the controlling section makes a determination that a cooling capacity of the refrigeration apparatus has been reduced, and outputs an anomaly signal indicating the determination, wherein the controlling section includes a receiver configured to receive determined temperature and humidity values representing a temperature and a humidity determined in the test chamber, set temperature and humidity values representing a preset temperature and a preset humidity of the test chamber, the heating electric power value, and the humidifying electric power value, a stability determining section configured to determine that the temperature and the humidity in the test chamber are in a stable state when the determined temperature and humidity values keep matching the set temperature and humidity values, respectively, for a predetermined period of time, a data memory configured to store stable electric power values of the heating device and the humidifying device in the stable state when the stability determining section determines that the temperature and the humidity in the test chamber are in the stable state, and a comparison and determination section configured to compare the heating electric power value and the humidifying electric power value with predetermined reference electric power values of the heating device and the humidifying device, respectively for the determination, and output the anomaly signal, wherein