<p>In a vehicle seat system equipped with an active headrest mechanism (30) and a lumbar support (21), a load-receiving part (32) of the active headrest mechanism (30) is positioned behind the lumbar support (21) as viewed from front of the seat. The vehicle seat system is arranged so that when a specified amount or more of load is applied from front of the seat to a lumbar support plate (22) of the lumbar support (21), one end part of a plate support member (23) supporting the lumbar support plate (22) exits from an insertion hole (17) provided at a side frame (4) to disengage from a seatback frame (2), and the disengaged end part of the plate support member (23) then abuts on the load-receiving part (32).</p>
