The rotation direction detection device 1 includes a current detection unit 11 that detects a direction of a current flowing through the motor 3, a voltage detection unit 12 that detects each voltage before and after the motor 3 in the power supply line 4, and a direction of the current and a direction before and after the motor 3. A rotation direction detection unit 13 that detects the rotation direction of the motor 3 based on each voltage. The current detector 11 is connected to points A and B before and after the shunt resistor 5, detects the direction of the current flowing through the power supply line 4, and forms current direction information CI. The voltage detection unit 12 is connected to points A and C before and after the motor 3, detects the voltage at each position, and forms motor terminal voltage information VI. The rotation direction detection unit 13 detects the rotation direction of the motor 3 based on the logical combination of the current direction information CI and the motor terminal voltage information VI.
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