Disclosed herein is a body frame for a bicycle which is able to provide higher strength in such a way to use a carbon material even when the outer diameters of a top tube, a bottom tube, a seat tube, a chain tube, etc. have the thickness of a body frame of a classical bicycle, while relatively reducing the weight of the body frame. For this, the body frame for a bicycle according to the present invention is configured in such a way that each of the top tube, the bottom tube and the seat tube is made in a circular shape wherein the outer diameters are same from one end to the other end of each tube, and the flesh thickness of each tube is relatively thicker at the other end portion than one end portion, and each tube is made of a carbon material.