Аннотация:The demand of CFRP (Carbon Fiber Reinforced Plastics) has been become heavy for its light weight and high strength. However it is a problem that the machining cost becomes high because the tool life is very short. The objective of this research is to clarify the tool wear mechanism on the milling of CFRP. Therefore the influence upon tool wear by the fiber orientation of CFRP was focused on. Then tool wear and cutting force were measured during the milling of the CFRP which has the unidirectional fiber orientation. As a result of the experiment, the relationship between tool wear and fiber orientation of CFRP was made clear. When feed rate was 500 mm/min, for example, tool wear increased because number of cut fibers increased when angle between feed direction and fiber orientation was about 45 degrees. On the other hand, tool wear was reduced by low number of cut fibers when the angle was about 0 degrees. In addition, tool wear model that based on the experiment was proposed. Number of cut fibers and fiber cutting angle varied according to fiber orientation were considered in the model. Then the model was validated comparing with the experiment.