PURPOSE: To enhance economical efficiency by preventing a waste material from its generation at the time of reoperation.

CONSTITUTION: At the time of stopping operation, a temperature of a heated object is measured by a temperature measuring device 12 in a plurality of parts of a conveying path and left as stored in a control part, and at the time of reoperation, by respectively independently controlling a plurality of unit coil parts 11a of a heating coil 11 corresponding to each temperature measuring device 12, the heated object 1 is heated to increase its temperature in accordance with the stored temperature and then restarted to be conveyed.