To efficiently perform storage in a closet part of an existing house, in a storage device.

A sliding door in the closet part of the existing house is removed, and metallic hinge seats 36 and 38 are installed by a rag on upper-lower surfaces 2-4 and 2-5 of a provided closet cavity part 4, and a hinge shaft 24 is installed between the hinge seats 36 and 38. Cylindrical parts 30A and 30B of hinges 26A and 26B of rotary doors 12A and 12B, are inserted into the hinge shaft 24 by a series of end part mutually abutting structure, and the rotary doors 12A and 12B are installed on the common hinge shaft 24. In the rotary doors 12A and 12B, its upper-lower ends extend up to the upper-lower surfaces 2-4 and 2-5 of the closet cavity part 4, and a cap 59 for blocking up clearance between the opposed ends of the rotary doors 12A and 12B in closing, is installed on the projecting end of the hinge shaft 24 from the hinge seats 36 and 38. The closet cavity part 4 is hidden by closing of the rotary doors 12A and 12B, and the closet cavity part is formed into a wall-like structure up to the ceiling from a floor.