To enable the common use of a joint member sealing jig for seal test if an inside diameter of a pipe passage of a joint member is the same by tightening a nut screw-fitted on a bolt and expanding an outside diameter of an elastic body provided between seat plates.

To apply a joint member sealing jig on a joint member 6, a sealing jig is inserted through an opening 6a side to which a hose of the joint member 6 to be used in a test is connected, and a nut 5 is tightened for a bolt 4. Then, an outside diameter of an elastic body 1 compressed by seat plates 2, 2 is expanded to be larger than the initial outside diameter so that a pipe passage 6b of the joint member 6 can be sealed. The joint member 6 in which the pipe passage 6b is sealed is formed as a connection body between a hose and the joint member 6 by fitting the hose externally through the opening 6a side for a seal test, and then aged treatment is applied to it in a constant temperature bath for the purpose of pretreatment of the seal test to conduct the seal test. Consequently, if an inside diameter of the pipe passage of the joint member is the same, the joint member can be used in common irrespective of its shape.