A seat belt apparatus includes a belt reel having a belt wound thereon, a motor for driving the reel to take up the belt; a control section for adjusting an amount of electric current supply to the motor to thereby control a belt-taking-up driving force of the motor, a current detection section for detecting the current supplied to the motor, and a rotation detection section for detecting a rotational position of the reel. The control section includes a constant current control section for executing a constant current control mode so that the current supply to the motor takes a target value, and a target current supply value change section for changing the target value when a detection signal from the rotation detection section has satisfied a predetermined condition in the constant current control mode.