PURPOSE: To facilitate the portability of a spare key by forming a through hole-like key receiving hole for receiving the spare key embedded therein in a card-like case having an outline dimension to be received in a license holder and providing pieces for covering both surfaces of the case.

CONSTITUTION: A case 1 is injection molded of a plastic material for an example to have an outline dimension receivable in a license holder and the thickness same as or slightly larger than that of a spare key 3 to be received. The case 1 is formed with a through hole-like key 13 receiving hole 2 consisting of a knob receiving part 6 and stem receiving part 7 corresponding to the general shape. Cover pieces 14, 15 made of thin plastic sheets are disposed on both surfaces of the case 1 to be bonded thereto so that the spare key 3 is received and held therein. Tackifier is previously applied to one surface of the cover pieces 14, 15 to which a parting agent is applied. Such cover pieces are glued to the case 1 after removing the parting agent.