A pipe connecting structure for connecting a pair of sleeve-like pipes integrally in an axial direction by inserting a male side end portion of one of the pair of sleeve-like pipes into an opening of a female side end portion of the other sleeve-like pipe so as to serve as a connecting portion, wherein a male side protrusion insertion hole and a female side protrusion insertion hole are formed in a peripheral surface of each end portion of a pair of the sleeve-like pipes which constitute the connecting portion, the protrusion insertion holes are brought into coincident with each other, an engagement protrusion is inserted in the protrusion insertion holes and engaged therewith, and such an engagement state of the engagement protrusion is retained by pressing the engagement protrusion with a sleeve member disposed in such a manner as to cover the connecting portion.