A motor device comprising: a rechargeable battery arranged in a battery pack, an electric motor configured to be operated when supplied with power from the rechargeable battery; a voltage detection unit (17, 23) configured to detect voltage of the rechargeable battery; a determination unit configured to perform an abnormality determination based on a comparison of the voltage of the rechargeable battery, which is detected by the voltage detection unit (17, 23), and a determination value (V1, V2); a control unit configured to control the operation of the electric motor in accordance with the determination result of the determination unit; and a temperature detection unit configured to detect the usage environment temperature in the battery pack, wherein the determination unit is configured to change the determination value (V1, V2) in accordance with the temperature detected by the temperature detection unit and perform the abnormality determination based on the changed determination value (V1, V2), the motor device being characterized in that the determination unit is configured to: perform an initial abnormality determination in a state immediately before the electric motor is operated immediately after an activation command; use, for the initial abnormality determination, a standard determination value; and change, during subsequent operation of the electric motor, the determination value (V1, V2) to the changed determination value in accordance with the temperature detected by the temperature detection unit. a rechargeable battery arranged in a battery pack, an electric motor configured to be operated when supplied with power from the rechargeable battery; a voltage detection unit (17, 23) configured to detect voltage of the rechargeable battery; a determination unit configured to perform an abnormality determination based on a comparison of the voltage of the rechargeable battery, which is detected by the voltage detection unit (17, 23), and a determination value (V1, V2); a control unit configured to control the operation of the electric motor in accordance with the determination result of the determination unit; and a temperature detection unit configured to detect the usage environment temperature in the battery pack, wherein the determination unit is configured to change the determination value (V1, V2) in accordance with the temperature detected by the temperature detection unit and perform the abnormality determination based on the changed determination value (V1, V2), the motor device being characterized in that the determination unit is configured to: perform an initial abnormality determination in a state immediately before the electric motor is operated immediately after an activation command; use, for the initial abnormality determination, a standard determination value; and change, during subsequent operation of the electric motor, the determination value (V1, V2) to the changed determination value in accordance with the temperature detected by the temperature detection unit. perform an initial abnormality determination in a state immediately before the electric motor is operated immediately after an activation command; use, for the initial abnormality determination, a standard determination value; and change, during subsequent operation of the electric motor, the determination value (V1, V2) to the changed determination value in accordance with the temperature detected by the temperature detection unit.