PURPOSE: To reduce the weight and size of a connecting rod by bending steel plates having an adequate shape in the same direction to form a pair of half split body parts then uniting and joining the body parts to one body thereby forming the lower part into a hollow state.

CONSTITUTION: Steel plates 9 formed by pressing, etc. into a suitable shape are bent upward at a line X-X and a line Y-Y to form respectively the half split body parts 2L, 2R of the connecting rod. Semicircular recesses 12, 13 (not shown in fig.) for contouring a large end hole 3 and a small end hole 5 are formed in this stage. The recesses 12, 13 are then butted to each other and contact parts 14, 15 thereof are welded by an arc, laser beam, etc. Since flanges 17, 18, 19 are formed around track-shaped holes 10, 11, the hollow part is constituted in the lower part of the joined and united connecting rod and the strength of the body is improved. The reduction in the weight and size of the connecting rod is thus made possible and the cost is reduced as well.