A method of forming an organic film according to one embodiment, includes: forming an organic film on a substrate with a pattern forming material; patterning the organic film to form a patterned film; and supplying a precursor of a metallic compound to the patterned film to form a mask pattern. The material contains a polymer having a side chain including an unshared electron pair and a group having oxidation activity to the precursor. The group includes at least one group selected the group consisting of a carboxyl group, a hydroxyl group, a sulfo group, and a nitro group. An average number of the group per monomer unit is 0.3 or more. The metallic compound contains a metal with an atomic number of 22 or more in group 3 elements to group 13 elements.