To perfectly eliminate malfunction between a pipe holding member when holding a resin pipe, to prevent the generation of damage in a surface of the resin pipe due to the pipe holding member to perfectly eliminate leakage of water in the surface, and to reduce resistance as much as possible when inserting the resin pipe.

In the pipe holding member 2 to be used for a one-operation type fitting for resin pipes, the pipe holding member 2 is formed of an annular part for holding the whole shape, slit parts along the longitudinal direction of the resin pipe, and craw parts projecting inside between the slits. The inside diameter of the craw part 4 at a central part 4a is formed smaller than the outside diameter of the resin pipe 10 by 0.3 to ±0.1 mm, and the inside diameter of the craw part is formed into a circular diameter having a curvature larger than that of the outside diameter of the resin pipe 10.