A sensor device and a sensing method capable of detecting even a small external force are provided. A sensor device includes: a backflow prevention unit provided in the middle of a circuit that supplies a current from a power supply unit to a motor unit; a potential detection unit configured to detect each of potentials at a preceding stage and a subsequent stage of the backflow prevention unit; and an external force detection unit configured to detect an external force applied to a member connected to the motor unit on the basis of the potentials at the preceding stage and the subsequent stage of the backflow prevention unit.