At the lancet device (10), a structure is used as a shot prevention mechanism for preventing re-shooting using a used lancet (20), that inhibits movement to a shot-ready completion state where a puncture body (23) is held at different positions within a casing (22) before and after use. The holding position of the puncture body (23) within the casing (22) before and after use being different is then utilized. When the used lancet (20) is fitted to a main body (30), a stopper plate (38) does not operate, and a setting release button (37) remains in a pressed down state and is not pushed up.
