A method of manufacturing a spline telescopic shaft includes a masking step in which, in a prescribed axial-direction region of an intermediate manufacturing product, partial tooth grooves that are equally spaced circumferentially are respectively covered by masking members that are equally spaced circumferentially; a resin coating step in which a resin layer is formed, and inner surfaces of the partial tooth grooves covered by the masking members are left as metal exposed portions that are equally spaced circumferentially; and a coating film forming step in which, in a state where the intermediate manufacturing product provided with the resin layer is centered with respect to a broach via the metal exposed portions, the intermediate manufacturing product and the broach are caused to slide relative to each other in an axial direction by press-fitting such that the resin layer is shaved to form a resin coating film.