A seat belt device includes a belt reel on which a webbing is wound, an electric brush motor for driving the belt reel, a motor control part that performs drive control of the electric brush motor, a voltage detecting part that detects a voltage generated between both terminals of the electric brush motor, and a failure determining part that determines whether the electric brush motor has failed or not on the basis of the presence or absence of a voltage having a frequency component caused by the drive control of the electric brush motor that is detected by the voltage detecting part while the electric brush motor is driven by the motor control part.