Fluid device

A fluid device including a passage which is to be sealed by insertion of an annular gasket, the device comprising:

• a flow port open to form one end of the passage;
• and
• an annular groove arranged along an outer circumferential edge of the flow port, the annular groove being open so as to insert the gasket therein,
• wherein:
• the annular groove has a radially-inner side interior wall and a radially-outer side interior wall,
• the radially-inner side interior wall having includes:
• a first tapered portion which includes an open end of the annular groove and which slopes radially outward from the open end of the annular groove in a depth direction, and
• a first portion that is continuous with the first tapered portion in the depth direction, extends to a bottom portion of the annular groove in the depth direction, and has a larger diameter than the first tapered portion,
• the radially-outer side interior wall includes:
• a guide extending throughout a predetermined range from the open end of the annular groove and having a diameter that is larger than a diameter of an outer circumferential surface of the gasket, and
• a second portion that extends to the bottom portion in the depth direction and has a smaller diameter than the guide, and
• a thickness of the gasket in a radial direction is larger than a width between the first portion and the second portion.