Provided is a contact hole forming method, wherein in a thermal flow step the contact hole size can be fixed after thermal flow even if the resist material lot changes, or, wherein at the same bake temperature the contracted size, namely the flow amount, can be fixed. More specifically, provided is a contact hole forming method comprising a step of coating a resist material onto a substrate, a step of heating the coated resist material, a step of exposing the heated resist material to light through a photo mask adapted for a contact hole pattern, a step of heating the exposed resist material, a step of forming the contact hole pattern subsequently by developing with a developing fluid and a step of thermal flow treatment for heating the obtained contact hole pattern, wherein the resist material comprises an organic compound which does not react with the other components within the resist material and does not change a resolution property, and wherein when the resist material lot is changed, an amount of the organic compound to be added is changed so as to keep the contact hole pattern identical before and after the lot change.