SEALING STRUCTURE AND ASSEMBLING METHOD OF SEALING STRUCTURE

A sealing structure capable of providing consistent sealing performance for a prolonged time, and an assembling method of the sealing structure. An installation component is provided with an annular fitting groove in which a resin gasket is mounted. The fitting groove has a bottom with an annular projection including a tapered surface increasing in a diameter thereof from a pressure side to a non-pressure side, and a tapered surface decreasing in a diameter thereof from the pressure side to the non-pressure side. The tip of the annular projection is positioned closer to the pressure side than a center in a width direction of the fitting groove.