To regulate the interval between an ultrasonic horn 1 and an anvil 2 at the seal position with high precision in an ultrasonic sealing device of the type in which the ultrasonic horn 1 to generate ultrasonic vibration and the anvil 2 are disposed facing each other, and advanced/retracted between the evacuation position and the seal position.

The ultrasonic sealing device comprises a main lever 12 which is connected to a driving rod 9 and oscillated, a transmission mechanism which converts the oscillation of the main lever 12 into the straight movement and transmits it to the ultrasonic horn 1, a sub lever 15 which is connected to the main lever 12 and oscillated, and a transmission mechanism which converts the oscillation of the sub lever 15 into the straight movement, and transmits it to the anvil 2. The sub lever 15 is supported around an eccentric shaft 14 in an oscillating manner, and a worm wheel 42 is fixed to a supporting shaft 14a to support the eccentric shaft 14. When a worm 41 is rotated, the eccentric shaft 14 is rotated via the worm wheel 42, and the position of the center of oscillation of the sub lever 15 is moved. The interval between the ultrasonic horn 1 and the anvil 2 can be finely regulated thereby.