This ultrasonic welding device (1) is provided with: a rotating support mechanism that can rotate centered on a rotational axis (L1) a horn (14) and anvil (15) that weld a sheet (W) by means of sandwiching the sheet (W) supported by the rotating support mechanism an ultrasonic generator (16) connected to the horn (14) a drive shaft (4) extending from the rotating support mechanism to the base side a slip ring (8) provided to the base of the drive shaft (4) an electrical wire (C1) connecting the ultrasonic generator (16) and a rotating-side terminal (35a) of the slip ring (8) and a drive shaft support member (2) that rotatably supports the drive shaft (4) at a position between the slip ring (8) and the rotating support mechanism. The tip of the drive shaft (4) is disposed at a position between the tip (E1) and base (E2) of the rotating support mechanism, and the electrical wire (C1) is led through a through hole (4b) in the drive shaft (4) and from the slip ring (8) to the ultrasonic generator (16).
