To provide a method to manufacture an extraction bag by efficiently forming a continuous web into a cylindrical shape in a forming-filling process.

For the forming of a cylindrical web in a forming-filling process, a web is towed along a tapered guide 6, and then, towed along a forming tube 20 having a shaft which forms a small angle to a guide plate, and crosses with the guide 6, and by doing so, the forming is achieved. The web is pulled out at a forming tubular station by confronted driving rollers 24 (these rollers pinch the edge of the web), along the guide and the forming tube. Both side margins of the web are folded and superposed from the central part of the web. The central part of the web moves on the guide plate, but side edges are brought together (joined) after reaching the forming tube. The driving rollers 24 or sealing rollers 26 form a closed cylinder by sealing the edges along the forming tube.