There are provided a seatback supporting backs of plural passengers seated on a bench type of seat cushion, a headrest provided at an upper portion of a first portion of the seatback and supporting a head of the passenger seated in front of the first portion, a pressure-receiving portion provided at a second portion of the seatback which is arranged beside the first portion so as to move rearwardly when being pressed by a rearward move of the passenger seated in front of the second portion, and a headrest moving mechanism provided to connect the pressure-receiving portion to the headrest so that the headrest is moved forwardly or upwardly in accordance with a rearward move of the pressure-receiving portion. Accordingly, the passenger's head can be protected with a simple structure.