To provide a card key, in which a key plate is machined simply, slipping-off can be prevented surely and the mounting workability of the key plate is also improved.

In this card key 1, a tabular key plate 3 is fitted detachably to a tabular card case 2 made of a synthetic resin. A holding section 2a, in which the key plate 3 is mounted on the surface side, is formed to the card case 2. The holding section 2a has recessed sections 2b, 2c and an opening section 2d, and elastically deformable engaging projecting sections 2f engaged and disengaged with and from one surface side of the key plate 3 are formed on the surface side of the peripheral section of the opening section 2d.