A holding structure (2) in an ultrasonic vibration welding device that welds workpieces by applying ultrasonic waves to the workpieces holds an ultrasonic vibration transmitter (horn) (5) bearing the transmission of longitudinally vibrating ultrasonic waves in holding members (8, 8). The horn comprises a horn body (51) having the length of one-half the wavelength λ of the ultra-sonic vibration. Holding structure (2) includes holders (7x, 7y) having a prescribed volume and thin sheet connectors (6a, 6b) placed at different positions (Pa, Pb) on the horn body (51). The horn body (51) is fixed to holding members (8, 8) by means of the respective holders (7x, 7y).