A frame for motorcycles includes a first frame section having a head pipe portion that supports a front fork and a second frame section having a pair of rear arm brackets that support a rear arm and are arranged away from each other in a direction along a vehicle breadth. The first frame section includes a gusset portion having a hollow closed, cross sectional shape and formed with an opening, which is opened rearwardly of the head pipe portion. The rear arm brackets, respectively, include a connection end having a cross sectional shape to be opened inward in the direction along the vehicle breadth, and extending toward the gusset portion. The connection ends of the rear arm brackets are welded to an edge of the opening of the gusset portion.