To provide a method for manufacturing and reforming a car body frame by unitizing and combining existing car body frames.

In the method for manufacturing a car body frame, car body frames of two-wheel, three-wheel, or four-wheel vehicles are separated, unitized and combined with each other. Since the connecting method, position, or quantity can be freely set among the units of the car body frames, a novel commuter can be composed by combining a front part unit of a two-wheel vehicle with a rear part unit of a four-wheel vehicle, for example.