To provide technology of installing and constructing an interior door pocket, by which a sliding door or the like is neatly stored in the interior wall of primarily a nursing home or the like, or other buildings such as a condominium, a hospital or the like.

A plurality of plate-like steel bands (2) bent in the form of a downward U-shape are riveted on the upper part of a door pocket rail unit (1). Further, a plurality of the plate-like steel bands (2) bent in the form of the downward U-shape are riveted on the upper part of a door pocket unit (3). Next, the door pocket rail unit (1) having the bands is inserted into the door pocket unit (3) having the bands with the dimension (6) of the sliding door left outside, and fixed in place with screws or the like (4) together with other accessories. A steel door pocket (5) is configured as described above. Lastly, the plate-like steel bands (2) of the steel door pocket (5) are bent again in the form of an upward U-shape, and the steel door pocket (5) is installed in the building frame (7) using the plate-like steel bands (2) fixed with the screws or the like (4) from both the sides of the building frame (7).