A helical winding unit includes a plurality of guides arrayed in a peripheral direction of a liner, and adapted to guide each of a plurality of fiber bundles supplied to the helical winding unit to the liner, and an opening member arranged downstream of the plurality of guides in a travelling direction of the fiber bundle, and including an inner peripheral surface for forming a hole, through which the plurality of fiber bundles are inserted from one side to the other side in the axial direction. A plurality of opening surfaces on which the plurality of fiber bundles travel while making contact are formed on the inner peripheral surface of the opening member, and a cross-sectional shape orthogonal to the axial direction of each opening surface is linear.