Al-bronze casting have recently been used as materials for propeller shaft sleeves of small and medium size ships because Al-bronze has an excellent cavitation erosion resistance; while Sn-bronze castings used for the sleeves because of it's good wear resistance. However, in several ships having shafts with Al-bronze sleeves, wear down of lignumvitae bearings was remarkable, and some of the bearings had to be renewed in 6 months. The authors assumed that the Al-bronze has specific nature of wearing the lignumvitae bearings, and have carried out the experiments to investigate the comparative wearing nature of Al-bronze and Sn-bronze against lignumvitae. The results obtained are summarized as follows: (1) The wear resistance of lignumvitae depends on the metallurgical property of a sleeve materials, the main factors being chemical composition and microstructure. (2) In the case of Al-bronze, sleeve alloy powders formed by sliding wear lignumvitae face mechanically. (3) In Sn-bronze sleeves, oxide film formed between the surface of lignumvitae during decreases the wearing speed. (4) These phenomena depend on sliding load.