A vehicle seat comprises a rectangular-shaped seat back frame having right and left side frames; a flexible plate member provided between the right and left side frames; a seat back cushion provided in front of the flexible plate member; a mechanism for pushing the seat back cushion to a front direction by forwardly protruding the flexible plate member that results from the flexible plate member being bent; a headrest for supporting a head of a seat occupant, wherein the headrest is forwardly movably connected to the right and left side frames via right and left link members; and a rear-end collision detecting plate disposed at a portion of the seat back frame behind the seat occupant, wherein the rear-end collision detecting plate detects rearward movement of the seat occupant.