PURPOSE: To execute carburization to a steel sheet in good condition without needing an atmosphere having high carbon potential by inserting a foil-like carburizing agent between the steel sheets, heating in a furnace and carburizing.

CONSTITUTION: The carbon steel sheet 7 for machine structural use wound in feeding rollers 4, 5 arranged at out of a furnace in one side is fed in an atmospheric heating furnace 1 and wound with winding rollers 4', 5' arranged at out of the furnace in the other side. At this time, the another roller 6 winding the foil-like carburizing agent 8 near the rollers 4, 5 is arranged, and the steel sheet 7 is heated in a heating furnace 1 at about 5min so as to insert this carburizing agent 8 between the upper and lower steel sheets 7. Then, as the foil-like carburizing agent, material, which a newspaper is dropped into Ba(OH)2 saturated water solution (about 40°C) and dried, is used. By this method, without adjusting the carbon potential in the carburizing atmosphere, good carburization is executed to the steel sheet 7 in a short time.