Abstract: A drying apparatus includes a thermal roll for contacting and heating aluminum web in a continuous sheet form. The thermal roll includes a roll surface, having a static friction coefficient ? defined by contact with the web. The static friction coefficient ? satisfies a condition of: t+V?G wherein ? G = ? ? · ? A ? ? 1 = ? ? · t · sin ? ( ? / 2 ) where t is tension applied to the web; G is roll retaining force with which the roll surface frictionally retains the web; V is thermal expansion force generated by thermal expansion of the web retained on the roll surface; ?A1 is pressing force caused by the tension to the web and applied to the roll surface by the web; ? is a wrap angle at which the web contacts the roll surface. Thus, distortion of the web can be prevented even with a great difference in the temperature from the thermal roll.