The invention relates to a rectangular key case having a swing-out flat key, so that the key can be integrated into the case in a space-saving manner. The case contains a key receiving space formed as a two-legged receiving shaft which, viewed over its length, is essentially L-shaped and extends with its longer leg along the side edge and with its shorter leg along the front edge of the key case housing. The flat key, in its non-working position, is lowered with its shank part entering into the longer leg and with its grip part entering into the shorter leg located near the corner of the key case housing. The shank part of the flat key is pivoted outside the housing and around its corner with the flat key in a working position pointed in the opposite direction from its non-working position and whereupon the grip part of the key engages into a longitudinal area of the shorter leg more remote from the corner.