PROBLEM TO BE SOLVED: To reduce amounts of drug solution adhering to surfaces of a cover and a female member after separating the cover from the female member, by improving adhesion between the cover and the female member.SOLUTION: A cover 90 comprises: a seal region 92 adhering to an outer peripheral surface of a male member 20； a deformable region 93 disposed on the tip side from the seal region 92； a slit 95 provided on the tip of the deformable region 93 so as to be penetrated by the male member 20； and a holding part 98 for holding the cover 90. The deformable region 93 is easier to perform compressive deformation and extension deformation than the seal region 92. A sealed space 99 is formed in the deformable region 93 in an initial state in which the cover is separated from the female member. The holding part 98 is provided in the seal region 92.
