A structure of storing a vehicular seat according to one aspect of the invention is constituted by a seat detachably connected to a support base, and a storing space capable of storing the seat detached from the support base. The seat includes an engaging member is fixed to the support base by engaging an engaging portion provided at the support base. The storing space includes a bottom wall, side walls erected to an upper side from two left and right side edges of the bottom wall, and a depth wall erected from a depth edge of the bottom wall to the upper side, and is constituted to slide to store the seat. The seat includes fixing means at predetermined positions inside of the storing space. The fixing means are formed by shapes to slidingly receive and to fix the engaging member of the seat.