At a medicament manufacturer B, a mouth of a vial body 11 or syringe cartridge 51, in which a medicament 16 is sealed with a plug, is enclosed using a cap 15 or 50 under an environment of a predetermined cleanliness (for example, class M6.5 (the JIS method) or higher). In advance of this enclosure, the cap 15 or 51 has been manufactured at a container manufacturer A by molding with a molding material, which is free of any powdery material, under an environment having cleanliness not lower than the predetermined cleanliness. A cap for enclosing a mouth of a vial body or syringe cartridge sealed with a plug and a manufacturing method of the cap can be provided accordingly.
