To provide a method and apparatus for manufacturing an endless belt from a molding difficult resin such as a composition in which a conductive filler such as carbon black is dispersed in a molding difficult matrix resin mainly containing a polyarylate.

The apparatus for producing the endless belt from a resin film containing the conductive filler has (a) a first ultrasonic horn 21 which has an annular groove 22 on a flat upper surface 21a and is rotated, a roll 24 which is engaged with the annular groove 22 and follows, an ultrasonic welding/fusing device having a conveyance stand 26 movable in the tangential direction of the first ultrasonic horn 21, and (b) an ultrasonic device having a contact stand 41 having a flat upper surface 41a and a second ultrasonic horn 42. Between the annular groove 22 of the first rotating ultrasonic horn 21 and the following roll 24, the protrusion of a resin film F is ultrasonically welded linearly through the protrusion of the resin film F and fused, and then an ultrasonic fusion part is flattened.