A seatbelt apparatus includes a deceleration detecting sensor for detecting a decelerating state of a vehicle and a controller for controlling the drive of a motor for the seatbelt apparatus corresponding to a detected value of the deceleration detecting sensor. The controller is provided with a correcting unit for correcting the detected value of the deceleration detecting sensor in anticipation of the future so as to advance the operational timing of the motor. By advancing the judgment timing for urgency so that the operational timing of the motor is hastened, it is possible to restrain a passenger's body in an emergency certainly without enhancing a restraining force of a webbing unnecessarily.