A motorcycle frame

A down tube (5) extending diagonally downwards from a head pipe (3) to the front of an engine (2) is an angular cross section pipe, with a rib being integrally formed in a front surface inner side, extending vertically. A lower half side of a rear surface section is made into a tapered section (62b) sandwiching the lower side, and a space (57b) is formed between this tapered section (62b) and front sections of the cylinder head (27) of the engine (2) and the cylinder head cover (28). A joint hose (34) constituting part of a water hose of a radiator (22), and an exhaust pipe (23), are arranged in this space (57b).