To form an inside corner part projecting inward the communication passage in the bending part or the confluent part in a pipe joint where the communication passage formed in the inner part has a bending part or the confluent part.

The pipe joint 1 is formed by an inner cylindrical body 2 forming an inner shape of the pipe joint 1, and an outer package body 3 integrally formed on the outer periphery of the inner cylindrical body 2. The inner cylindrical body 2 is manufactured so that the inside corner part 11 projecting inward the communication passage 10 is made to be in an arc shape by blow molding. Core pins 301a-301c are inserted in a flow passage 10 formed in the inner cylindrical body 2, and disposed in a cavity 23 of an injection molding mold 2. A molten resin to be the outer package body 3 is injected into the cavity 23 in such a state that the inner cylindrical body 2 except the inside corner part 11 formed in the arc shape is heated at the melting temperature.