Wedge wire bonding is a bonding technique using ultrasonic vibration in the semiconductor manufacturing process. Bonding is performed by applying a load and ultrasonic waves to the wire using a cemented carbide tool. After more than a hundred thousand bonding, Al from the wire adheres to the tool, and the tool itself wears out due to repeated bonding. Since the tool's wear reduces the bondability, clarifying the mechanism is essential to improve productivity. In this study, we observed the morphology and microstructure of the tool with Al adhesion and surface wear. It was found that Al adhered to the area where the vertical load on the tool was high during welding, and wear progressed in the area where the vertical load was relatively low. There was no reaction phase at the interface between the tool and the adhered wire. Aluminum oxide and aluminum were present in layers in the adhered wire, indicating that the adhered wires grew due to repeated wire adhesion and destruction process. Tool wear was related to fretting wear and plastic flow associated with wire deformation.