A lancet device (10) includes a shot prevention mechanism for preventing re-shooting using a used lancet (20), which 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. A holding position of the puncture body (23) within the casing (22) before use is different than a holding position after use. 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 depressed state and does not pushed up.