forming method according to the present embodiment as seen in fig3 the flow amount of the purge gas 151 supplied through the gas supply pipe 111 to the area p 2 changes depending on the time by the gas control unit 140 that is a plurality of periods of supplying the source gas 137 can be intermittently set by the gas control unit 140 in the process for forming the epitaxial film on the substrate 101 that has been heated the period for temporarily stopping supplying the source gas 137 by the gas control unit 140 can be set between the periods of supplying of the source gas 137 the period that the purge gas 151 increases is the same length as the period for stopping supplying the source gas 137 or less than the length while the source gas 137 is stopping in another example of the film forming method according to the present embodiment in this case the substrate 101 can be rotated at high speed while being heated and while slightly vibrating up and down in the period for increasing the purge gas 151 therefore the adhesion between the substrate 101 and the susceptor 102 can be prevented even if the thin film caused by the source gas 137 is formed between the substrate 101 and the susceptor 102 the supply of the.