Abstract: An oil repellent agent including a modified natural product having at least one hydroxyl group, wherein a hydrogen atom of the hydroxyl group is replaced with an R group represented by —Y—Z, wherein Y represents a direct bond, —C(?O)—, —C(?O)—NR?— or —C(?S)—NR?—, where R? represents a hydrogen atom or a C1 to C4 alkyl group); and Z represents a hydrocarbon group having 1 to 40 carbon atoms and optionally having a substituent or a polysiloxane. The natural material is a natural product other than starch and preferably is a monosaccharide, a polysaccharide, glycerin or polyglycerin. Also disclosed is a textile product to which the oil-resistant agent is attached, an oil-resistant paper and a method of treating paper with the oil-resistant agent.