Seat belt and movement control method thereof

A seat belt apparatus, comprising:

• an anchor unit provided on a lower portion of a first side surface of a seat and configured for allowing webbing of the seat belt apparatus to be locked thereto;
• and
• an anchor moving apparatus configured to move the anchor unit forwards and backwards thereof,
• wherein the anchor moving apparatus includes:
• a motor configured to provide rotational force;
• and
• a motion conversion apparatus configured to linearly move the anchor unit by converting rotation motion of the motor into linear motion of the anchor unit,
• wherein the motion conversion apparatus includes:
• a screw provided before and after the seat and configured to be rotated by the rotational force transmitted from the motor;
• and
• a carrier coupled to the anchor unit, including a screw hole formed in the carrier for the screw to be inserted into and engaged to the screw hole, and configured to move forwards and backwards together with the anchor unit according to a rotation of the screw,
• wherein an upper pulley is coupled to a shaft of the motor,
• wherein a lower pulley is coupled to the screw, and
• wherein the upper pulley and the lower pulley are coupled by a power transmission belt to transmit the rotational force of the motor to the screw.