A seat system, adapted for a motor vehicle, includes a portable device taken along with a user for sending at least identification information, an on-vehicle front seat, an on-vehicle actuator for actuating the front seat, a keyless control unit and a seat control unit. The keyless control unit communicates with the portable device to lock and unlock door locks when the identification information is authorized, and the seat control unit actuates the actuator to perform a walk-in function for changing a position state of the front seat for a passenger to easily get in a rear seat side compartment according to an operation of the portable device when the authorization is made.