To provide a closet underfloor storage device capable of easily storing a long-sized stored object and having sufficient storage capacity.

The closet underfloor storage device is provided with an opening 8 in a floor face of a closet A; a storage space 11a in an underfloor part directly below the closet; and a storage space 11b in an underfloor part long in a separating direction from a putting in-and-out opening of the closet A. The long-sized stored object B can be stored vertically being rotated within a storage space 11 utilizing the storage space 11b.