An apparatus (31) for correcting the bending of the molten resin includes a temperature-adjusting device (32) arranged surrounding an extrusion passage (12) for extruding the molten resin (8) of an extrusion die head (7) along the direction of extruding the molten resin (8), a measuring means (33) for measuring the horizontal position of the molten resin (8) extruded from an extrusion opening (20) of the extrusion passage (12), and a control means (34) for controlling the temperature-adjusting device (32) based on the results measured by the measuring means (33).