PURPOSE: To prevent the deposition of a paint to the back surface of a strip like substance by preventing a back-turning phenomenon, by providing blowoff nozzles to the back surface of the running strip like substance in parallel to blow off air toward the back surface end parts of the stip like substance.

CONSTITUTION: Blowoff nozzles 7 parallelly provided to the end parts of the back surface of a running strip like substance 1 in the width direction thereof blow off air supplied from an air supply apparatus through the chambers 6 integrated with the blowoff nozzles 7. The leading ends of the blowoff nozzles 7 are provided to the insides from the end surfaces of the strip like substance 1 and each distance thereof is 50mm or less while the blowoff angle of each nozzle 7 is set to a range of 15W75° and the flow speed of air is 8m/sec or more. By this mechanism, over-spray liquid droplets can be prevented from depositing to the end parts of the back surface of the strip like substance 1 without being affected by the curl of the running strip like substance 1.