Method of manufacturing connector

A method of manufacturing a connector that includes a first connection portion to be connected to a connection member in which a fluid flows, and a second connection portion to be connected to a pipe member in which the fluid flows, the method comprising:

• integrally molding the first and second connection portions with a resin, by using a first molding die having a molding portion for molding outer shapes of the first and second connection portions, a cylindrical second molding die inserted into the molding portion of the first molding die to mold a cylindrical insertion hole in which the connection member is inserted, and a circular core portion inserted into the molding portion together with the second molding die in a state where the second molding die is inserted into the core portion;
• separating the first and second molding dies so as to remove the molded first and second connection portions together with the core portion from the first and second molding dies, after the integrally molding;
• and
• dissolving the core portion in the first connection portion by using a solvent, so as to form a circular recess portion for arranging an O-ring, the recess portion being recessed from a peripheral surface of the insertion hole to a radial outside in the first connection portion.