A crawler having a crawler pin and a crawler bush having lubrication between the crawler pin and the crawler bush without lowering the strength of the crawler at the running time, thereby to prevent the creak or seizure, as might otherwise be caused at the running time. A metallic sliding member having an excellent wear resistance can be arranged in the clearance between the crawler bush and the crawler pin. The metallic sliding member can be capable of holding lubricating oil and/or a lubricant. In addition, the clearance between the core bush and the crawler pin can be narrowed, so that the resulting structure retains the imbalance load on both the crawler bush and the crawler pin.