A fixture fastens pipe joints 5 to multiple ports 35A, 35B, 36A and 36B that are arranged substantially in a line in a port block 4 attached to the valve body 6 of a change-over valve 1. The fixture comprises a metal fixture insertion groove 40 cut from one side of the port block 4 to a depth reaching the individual ports, a metal fixture 41 having multiple recesses 44 arranged along one edge thereof so as to come into engagement with the pipe joints 5 when inserted in the metal fixture insertion groove, and bolt s 48 for fastening the metal fixture 41 and port block 4 to the valve body 6.