To provide a method for manufacturing body frames reducing the number of three-dimensional bending devices when many kinds of vehicles with different exterior design are produced.

The method for manufacturing body frames includes a frame cross-sectional shape setting step S1 setting the cross-sectional shape of frame members 2 constituting respective portions of the body frame 1 at a same shape with regard to respective body frames 1 of a plurality of vehicles with a same size and different external design, a middle member manufacturing step S2 manufacturing middle members 3 of a linear shape which become the origin of frame members 2 with the cross-sectional shape set in the step S1 for respective frame members 2, a three-dimensional bending step S3 forming the frame members 2 by performing three-dimensional bending work on the middle members 3 according to the shape of respective portions of the body frames 1 using the three-dimensional bending devices 50, and a body frame assembling step S4 respectively assembling the body frames 1 corresponding to the plurality of vehicles using the frame members 2 formed in the step S3.