A processing method for forming a structure including an amorphous carbon film includes performing a preliminary treatment of removing water from a surface of the underlying layer by heating the inside of the reaction chamber at a preliminary treatment temperature of 800 to 950° C. and supplying a preliminary treatment gas selected from the group consisting of nitrogen gas and ammonia gas into the reaction chamber while exhausting gas from inside the reaction chamber; and, then performing main CVD of forming an amorphous carbon film on the underlying layer by heating the inside of the reaction chamber at a main process temperature and supplying a hydrocarbon gas into the reaction chamber while exhausting gas from inside the reaction chamber.