Abstract: A vacuum sealing structure (1) for connecting a first connection part (13) with a second connection part (43) via a gasket (31). The first connection part (13) or the second connection part (43) is provided with a jaw (43a), having an end portion which is broadened outwardly of a pipe member forming a vacuum passage, and a support member (21) having an annular tapered groove (21a). The second connection part (43a) directly contacts the gasket (31) and a tapered groove (21a). Thus the second connection part tapered jaw (43a) is tightly pressed against the gasket (31) by fastening the support member (21) with a fastening member (15), thereby achieving a vacuum sealing structure for facilitating the sealing of a body (2) to be vacuum sealed. The body may be a viewing port (41). Since it is not necessary to secure the body (2) to a flange (21), welding for securing will not be required and no trouble will be caused with sealing.

Abstract: A ring-shaped metal gasket with the cross-section thereof being substantially rectangular shaped, with the ratio (t/w) of the thickness t of the ring portion to the width w thereof being in the range of 0.5 to 4, having a Vickers hardness in the range of 50 to 120; a vacuum flange for a metal gasket, including a sealing groove for receiving a metal gasket at the surface of the flange, the width of a cross section of the groove gradually decreasing in the direction of the depth thereof, an outer side wall section of the sealing groove being substantially perpendicular to the flange surface, and an inner side wall section of the sealing groove being inclined with respect to the flange surface, with a difference in level being provided so that the flange surface positioned to the inside of the sealing groove is lower than the flange surface positioned to the outside of the sealing groove, and a vacuum seal structure including the above gasket and flange are disclosed.