To form a suitable lubricating oil film between an inner circumference of a shaft hole of a small end of a connecting rod and an outer circumference of a piston pin.

In a lubrication structure for a piston pin 2 of an all-floating type connecting a connecting rod 1 with a piston 3, the connecting rod 1 is provided with a lubricating oil passage 13 extending toward a small end and in communication with a shaft hole 12 of the small end. An outlet 132 of the oil passage 13 is opened at a part biased along the circumferential direction of the shaft hole 12 from a central axis L of the connecting rod 1. A recess 21 is molded at a part facing the outlet 132 in the outer circumferential surface of the piston pin 2. Accordingly, the piston pin 2 receives an oil pressure of the lubricating oil reaching the shaft hole 12 of the small end through the lubricating oil passage 13 at the recess 21, and is constantly rotated in the shaft hole 12.