A puncture needle cartridge (1) includes: a lancet body (5) mounted with a puncture needle (3) on a front end side and having a mount (4) on a rear end side and a plate-like first case (6) and second case (7) covering the lancet body (5) from above and below and arranged slidably back and forth along each other. The puncture needle cartridge (1) is configured such that the first case (6) is slid forward of the second case (7), and in this slid state, the first case (6) and the second case (7) are secured to each other when ejected from the puncture instrument (10). This can make the puncture needle cartridge (1) impossible to mount again on the puncture instrument (10).
