A head pipe is disposed in a front side of a vehicle frame. Left and right main pipes extend from the head pipe toward a rear side of the vehicle frame. The Left and right main pipes are welded to the head pipe. A down tube extends from the head pipe toward the rear side and welded to the head pipe. The head pipe includes: a head pipe main body supporting a steering shaft; a main pipe connection portion disposed in a rear upper portion of the head pipe, the main pipe connection portion to which a front ends of the left and right main pipes are welded; and a down tube connection portion disposed in a rear lower portion of the head pipe. The head pipe main body, the main pipe connection portion and the down tube connection portion are integrally formed with one another by a casting or a forging. The down tube connection portion includes: an extension connection portion extending from the head pipe main body in a extending direction of the down tube; and a welding connection portion formed at a rear end portion of the extension connection portion, the welding connection portion to which a front end of the down tube is welded.