Gasket-mounting structure and gasket

A structure allowing a gasket to be mounted on a fluid device, comprising:

• the gasket including an annular attaching portion that has a first slope at an axial end;
• and
• the fluid device including an annular attached portion with a second slope that contacts the first slope;
• wherein
• the second slope at least partially includes a contact area that contacts the first slope to seal a gap between the first slope and the second slope;
• the contact area has an annular bulge protruding toward the first slope in contrast to other portions of the second slope so that the bulge is the earliest contact portion with the first slope when the contact area is brought into contact with the first slope;
• the attached portion of the fluid device comprises an annular protrusion extending toward the gasket:
• the protrusion includes an outer periphery with the second slope and an inner periphery facing a fluid channel,
• the protrusion has a tapering shape that tapers toward the gasket under the condition that the inner periphery has a curve convex to the radial inside of the attached portion, thus positioning a tip end of the protrusion at the radial outside of the inner periphery;
• and
• when the second slope contacts the first slope, the tapering shape of the protrusion form a hollow adjacent to the inner periphery of the protrusion and to the gasket.