PURPOSE: To provide a wire-bonding apparatus and method for controlling this apparatus capable of controlling the ultrasonic vibration output by accurately detecting a vibrational state of the tip part of a bonding tool by means of a compact construction without spoiling the characteristics of the wire- bonding apparatus on the basis of the detected result.

CONSTITUTION: A magnetostrictive film 20 provided on a bonding tool 12, to which vibration is transmitted from an ultrasonic vibrating element 16, is distored by the vibration of the bonding tool 12, and consequently the magnetic field around the magnetostrictive film is changed. The changed magnetic field is detected by a magnetic field detecting coil 30, and a control part 18 recognizes the vibration amount of the tip part of the bonding tool 12 on the basis of the detected magnetic field and controls the output of the ultrasonic vibrating element 16.