A tool change unit includes a base and two tool arms rotatably mounted on the base and respectively located on two sides of the base. Each arm body includes a position-returning element, a gripping element, and an actuation element. The position-returning element enables the tool arm to rotate for upward and downward moving between a first position and a second position. The gripping element functions to grip a main-axle tool or a magazine tool. The tool change unit is combinable with a power unit to form a tool change device. The power unit drives the tool change unit to do rotation or rotation and upward and downward movement.