The present invention provides a lancet assembly which eliminates the need to remove a resin cover encapsulating a pricking element. Upon inserting a lancet structure into a lancet holder, a force which separates a lancet cover encapsulating the sharp tip portion of the pricking element from a lancet body is generated, and this force is allowed to act on the lancet cover and the lancet body to thereby expose, within the lancet holder, the sharp tip portion of the pricking element encapsulated by the lancet cover and to locate the opening of the lancet holder in front of the sharp tip portion of the pricking element.