A fastening tool using a fastener of a type which is configured such that swaging is completed while an end region of a shaft part of a bolt remains integrated with the shaft part, and more particularly, a technique that may help provide a compact device structure while facilitating output management required for swaging, in the fastening tool. The fastening tool is configured to fasten a workpiece with a bolt and a collar without breaking a shaft part of the bolt, and a control part performs swaging operation while controlling the driving current of a motor to become a specified target current value and completes the swaging operation based on rotation speed of the motor.