There is provided an injector capable of launching a lancet to provide a pricking. The injector comprises a plunger part capable of launching the lancet in a pricking direction, and an injector casing, the plunger part being located in an interior space of the casing. The plunger part comprises a lancet-attachment portion in its tip, and the lancet-attachment portion has a dual cylindrical structure composed of an outer cylinder and an inner cylinder such that respective bodies of the outer and inner cylinders are spaced away from each other.
