A joint member is made of an elastic member whose cross sectional shape is an almost M-character shape and which has: an inserting portion formed with an opening portion and a slit; an outer edge portion as an outer peripheral portion of the joint member; and a supporting fixing portion for coupling the inserting portion and the outer edge portion on the upper portion side. A cross sectional shape of an opening of the opening portion is a shape of a circular cone frustum in which the opening and a bottom surface are coupled via an inclined surface. The slit is formed in the rectangular bottom surface. The joint member is sandwiched between a casing and a pressing plate. The inserting portion and the supporting fixing portion exist in planes which are different in the inserting direction of a liquid supply needle.