A method for processing a polysilazane film includes performing temperature increase of changing a process field of a reaction container, which accommodates a target substrate with a polysilazane coating film formed thereon, from a pre-heating temperature to a predetermined temperature, while setting the process field to be a first atmosphere containing oxygen and having a first pressure of 6.7 to 26.7 kPa. Then, the method includes performing a first heat process for obtaining an insulating film containing silicon and oxygen by baking the coating film at a first process temperature not lower than the predetermined temperature, while setting the process field to be a second atmosphere containing an oxidizing gas and having a second pressure higher than the first pressure.