A lancet device is configured for performing a puncture by mounting a lancet including a puncture needle to the tip of a puncture body holder. The lancet device has a simple configuration that makes it possible to strengthen the retaining force for retaining the lancet when the lancet is used. In the lancet device, an insertion portion of a puncture body that is inserted into a mounting portion of the puncture body holder is retained by means of the frictional force. A fastening member provided in a main body side makes contact with the outer peripheral portion of the mounting portion of the puncture body holder and inwardly fastens the mounting portion when the fastening member is moved in the puncture direction relative to the puncture body holder.
