To provide a lightweight and thin key accessory having locking confirmation function, which allows a user to confirm locking at any time while he/she is out, dispenses with a battery and causes no breakage or failure by impact of falling or the like.

A holder 1 with two closed sides made of a material not broken by impact includes a slide opening 3, indications 6 and 7 allowing discrimination of locking state, which is provided at ends of the opening, and a fastener 5 capable of easily releasing closing of an opened long side end. A key body 4 is inserted into the holder, and a ring 2 is inserted to the slide opening and a hole at a tongue portion of the key body to integrate the holder to the key body. In locking, the ring is slid in the direction of operation A, and an insert portion of the key body is exposed and inserted to a key hole. After locking, the insert portion of the key body is rotated around the axis of the ring at 180° in the direction of operation B to open the fastener, and the key body is housed in the key body. At that time, the ring is left at the indication of closing to mean a trace of locking. Thus, locking or not can be confirmed by confirming the position of the ring.