Disclosed herein are an apparatus and a method for diagnosing a fault of a multi-sensor of a motor. The apparatus includes: a plurality of tachometers attached to the motor to measure rotation speeds; and a plurality of processors each connected directly to the plurality of tachometers to receive the measured rotation speeds, thereby securing a plurality of directly obtained rotation speeds, sharing the obtained rotation speeds with each other, thereby obtaining a plurality of indirectly obtained rotation speeds, and performing a fault diagnosis on the plurality of tachometers using the plurality of directly obtained rotation speeds and the plurality of indirectly obtained rotation speeds.