According to one embodiment, a planarizing method is proposed. In the planarizing method, a surface to be processed of an object to be processed including a silicon oxide film is planarized in a processing solution by bringing the surface to be processed into contact with or close proximity with the surface of a solid-state plate on which fluorine is adsorbed. The bonding energy between fluorine and the solid-state plate is lower than that between fluorine and silicon.