A temperature monitoring device, monitoring a temperature of a motor control device that controls an action of a motor, wherein the temperature monitoring device comprises: a current value acquisition portion that acquires a current value supplied for the motor; a calorific value inference portion (20, 20); Wherein the calorific value inference portion (20, 20') infers a calorific value of the motor control device through a first thermal model as a first calorific value, the first thermal model indicating a relationship between the current value and the calorific value of the motor control device; and an anomaly judgment portion that compares the first calorific value inferred by the calorific value inference portion (20, 20') with a specified first threshold, so as to judge whether the motor control device has heating anomaly, the temperature monitoring device being characterized in that the calorific value inference portion comprises: a stop time multiplication portion (252, 253, 254); a thermal resistance ratio multiplication portion (203, 206, 208); and a switch (271, 272, 273), and wherein when a speed of the motor is detected to be below a specified value, the switch (271, 272, 273) is controlled to connect the thermal resistance ratio multiplication portion (203, 206, 208) with the stop time multiplication portion (252, 253, 254), to obtain the calorific value of the motor control device according to the thermal resistance ratio multiplication portion (203, 206, 208) and a current value in the stop time multiplication portion (252, 253, 254). a current value acquisition portion that acquires a current value supplied for the motor; a calorific value inference portion (20, 20); Wherein the calorific value inference portion (20, 20') infers a calorific value of the motor control device through a first thermal model as a first calorific value, the first thermal model indicating a relationship between the current value and the calorific value of the motor control device; and an anomaly judgment portion that compares the first calorific value inferred by the calorific value inference portion (20, 20') with a specified first threshold, so as to judge whether the motor control device has heating anomaly, the temperature monitoring device being characterized in that the calorific value inference portion comprises: a stop time multiplication portion (252, 253, 254); a thermal resistance ratio multiplication portion (203, 206, 208); and a switch (271, 272, 273), and wherein when a speed of the motor is detected to be below a specified value, the switch (271, 272, 273) is controlled to connect the thermal resistance ratio multiplication portion (203, 206, 208) with the stop time multiplication portion (252, 253, 254), to obtain the calorific value of the motor control device according to the thermal resistance ratio multiplication portion (203, 206, 208) and a current value in the stop time multiplication portion (252, 253, 254). a stop time multiplication portion (252, 253, 254); a thermal resistance ratio multiplication portion (203, 206, 208); and a switch (271, 272, 273), and wherein when a speed of the motor is detected to be below a specified value, the switch (271, 272, 273) is controlled to connect the thermal resistance ratio multiplication portion (203, 206, 208) with the stop time multiplication portion (252, 253, 254), to obtain the calorific value of the motor control device according to the thermal resistance ratio multiplication portion (203, 206, 208) and a current value in the stop time multiplication portion (252, 253, 254).