A method and device for preventing a flexible tubular belt from twisting for use in a tubular belt conveyer are disclosed. A flexible tubular belt is extended between first and second rollers, positioned at a certain distance away from each other, on which the tubular belt is opened, and the belt moving between the two rollers in the tubular form is supported by sets of support rollers which are radially arranged around the peripheries of the belt in contact therewith and are rotatably mounted to support frames. Twisting of the belt is prevented by means which varies an angle of a correction roller extending in a direction substantially perpendicular to the direction of movement of the belt in contact therewith. The correction rollers may be disposed in contact with the bottom and/or sides of the belt.