Disclosed is a safety belt system for vehicle seats, including: a vehicle seat part which includes a seat portion, and a backrest; a safety belt which includes a shoulder belt, and a waist belt, and restricts a body of an occupant; a headrest which is connected with the backrest by a rotation shaft, and protects a face or neck region of the occupant from the shoulder belt using a cushion having both convex sides; a sensor which senses impact of the vehicle; and a rotation locking unit which prevents the headrest from being rotated when the sensor senses an accident signal that is equal to or greater than a predetermined output.