To prevent furniture from tipping over and articles from dropping in an earthquake and to enhance the appearance of the interior in everyday life by installing, between an existing piece of furniture placed indoors and a ceiling that are different in height, a cabinet whose height is adjusted to match the space between them, and integrating the cabinet with the existing piece of furniture so that no space exists between the indoor floor and ceiling.

A cabinet is formed by inserting the side plates of lower 1 and upper 2 boxes into upper and lower grooves in the side plate of a middle box 3, respectively, and supporting them against a plurality of retaining columns 5 each cut to a predetermined height. In this case, the retaining columns 5 are held by a central socket 6 and end sockets 7. The cabinet is secured to the top of an existing piece of furniture with wood screws, etc., so that it is integrated with the existing piece of furniture. A folding door 4 in which folding parts 12 alternate and are molded integrally is mounted in an opening in the front of the cabinet.