A puncture device capable of preventing needle stick accidents and of reducing the burden on patients during operation. In this puncture device, a puncture needle cartridge comprises: a lancet body having a puncture needle at one end with the other end being to be held by a puncture instrument body a protective cap and a puncture needle holder engaged with the lancet body to rotate together with the lancet body about a rotation axis P. A mounting member rotates together with the puncture needle holder with a boss guided by a slit through being pressed by the puncture needle cartridge in a direction of mounting in a case, and is mounted in the case. The protective cap, formed integrally with the lancet body, is prevented from rotating by being grasped and is separated from the lancet body with the rotation of the mounting member.
