PURPOSE: To prevent the generation of crack and the resultant influence by providing a thick wall part surrounding the outer area of the outer circumferential edge of an oil hole at the outer circumferential face of a bearing part, and an oil sump part with a concave shape surrounding the outer area of inner circumferential edge of oil hole at the inner circumferential face of bearing part.

CONSTITUTION: At a piston pin bearing part 2 formed at a small edge part of a connecting rod 1, an oil hole 6 is formed in a disc head shape penerating the bearing part in the radial direction, and a thick wall part 7 is formed at an outer circumferential face 2A to surround the outer area of outer circumferential edge of the hole 6 and extend over the whole bearing width. An oil sump part 8 with a concave shape in a circumferential long circular form is formed at an inner circumferential face 2B to surround the outer area of inner circumferential edge of oil hole 6. With this constitution, the generation of crack and the resultant influence can be prevented surely, thereby improving durability.