Disclosed is a substrate treatment method intended for a substrate having, on its surface, a composite product of an inorganic material containing silicon oxide and an organic material containing carbon and fluorine. The method comprises: an ultraviolet ray treatment step for irradiating the surface of the substrate with ultraviolet ray to remove a part of the organic material; a hydrogen fluoride processing step which is conducted after the ultraviolet ray processing step and which is for supplying a steam of hydrogen fluoride onto the surface of the substrate to remove at least a part of the inorganic material; and a heating processing step which is conducted after the ultraviolet ray processing step and which is for heating the substrate to cause the shrinkage of a part of the organic material that remains unremoved.