To facilitate efficient working of providing a film, and to improve the yield.

A body 12 constituted of a thermoplastic resin of an upper reservoir forming body 11 is provided with a ringlike projection 41 formed thereon to be protruding in a direction perpendicular to the lower reference face 12b. The ringlike projection 41 demarcates a channel opening 44 opened perpendicularly to the lower reference face 12b. The channel opening 44 is closed by a film 14 which is welded to the tip portion of the ringlike projection 41. A rib 45 protruding perpendicularly to the lower reference face 12b is formed on the body 12. A protruding height of a first region 46 coupled to the external wall face 41b of the ringlike projection 41 at the rib 45 is small than that of the ringlike projection 41.