A method for producing a modified lignin, including reacting one or more kind of a second generation ethanol fermentation residue and a second generation ethanol saccharification residue, with a phenol compound, a modified lignin having a ratio ((2H+G)/S) of a total of twice of a relative existence ratio H (%) of an H-type skeleton and a relative existence ratio G (%) of a G-type skeleton with respect to a relative existence ratio S (%) of an S-type skeleton, obtained from integrated values measured by 31P-NMR, of 2.5 or more, and an existence ratio of an aliphatic hydroxy group obtained by the same method of less than 20%, and a modified lignin-containing resin composition material.