A seatback-folding device for emergency escape for vehicles is equipped with a simply structured mechanism for emergency escape. A locking operation at the time of unfolding of a seatback of a second-row seat and an unlocking operation at the time of folding of the seatback of the second-row seat are performed by ascending/descending of a shaft caused by operation of a lever, thereby not only enabling an occupant sitting on a third-row seat to quickly fold the seatback of the second-row seat and thus to easily secure an emergency escape route, but also reducing the number of components, weight, the number of assembly processes, and manufacturing cost compared to a related art.