To provide a sealing member of high reliability prevented from inclining during vacuum filling while securing sufficient interference by forming the sealing member in flat shape.

In this sealing member, a cross section S cut at a plane passing the axes of a connecting cylinder 22 and a connecting hole 13 presents barrel shape in which flat parts 32c, 32d with prescribed length C, D almost perpendicular to linear parts 32a of an ellipse 32 are provided at circumferential parts 32b of the ellipse 32, and a distance A between the circumferential parts on a straight line passing the center Sc of the cross section S is longer than a distance B between the flat parts. The flat parts 32c, 32d respectively come in contact with the connecting hole 13 and connecting cylinder 22.