To reduce the number of parts and cost by providing a shaft-like projection on a holding member for storing an electronic part, and inserting the projection in a locking hole of a shank part to caulk the end part in fitting an electronic part to the shank part of a key plate.

A synthetic resin holding member 4 where an electronic part 2 such as a transponder or the like is stored in a receiving hole 3 of a shank part 1a of a key plate 1 which is formed by blanking a metallic plate is installed and fixed by inserting a shaft-like projection 11 in a locking hole 12 and caulking the end part of the projection 11. Subsequently, the shank part la is covered by molding to form a key for operating an ignition switch to which an immobilizer system is applied. At the time of molding, the holding member 4 is kept from being detached from the shank part 1a. The holding member 4 can be fixed by an eyelet, a rivet or the like instead of the shaft-like projection 11. Thus, the number of parts is reduced and assembling is facilitated so as to reduce the manufacturing cost.