Patent ID: 8863973

Claim:
A sealing structure comprising: an insertion member having a columnar outer shape; a cylindrical inserted member that is formed integrally with a filling chamber body in which a fluid is filled, and inserted with the insertion member; an O-ring that is accommodated in an accommodation region formed by an inner peripheral surface of the inserted member and an outer peripheral surface of the insertion member, and prevents the fluid from leaking, in a state where the insertion member is inserted into the inserted member and assembled coaxially with the inserted member; and one or two backup rings which are accommodated on both sides or axially outward of the O-ring in the accommodation region, and restrict a movement of the O-ring, wherein the insertion member and the inserted member are partially formed with assembling parts to be fitted or screwed to each other when they are assembled, and a first pressure release groove is formed in the axial direction so as to extend at least on the inner peripheral surface of the inserted member between the assembling part and the accommodation region, and communicates with an external space via a gap between the assembling parts.