To provide a dyeable resin composition having enhanced color development of dye, excellent durability and water resistance of dyeing.

This dyeable resin composition is obtained by copolymerizing a monomer composition containing a monomer A of 5-85 wt% selected from a monomer represented by formula (I) and a monomer represented by formula (II) and a monomer B of 15-95 wt% selected from a monomer represented by formula (III) and a monomer represented by formula (IV) (wherein R1 is a hydrogen atom or a methyl group, R2 is a 1-8C alkylene group, R3 and R4 are each a 1-4C alkyl group, R5 is a 1-4C alkylene group, Z is an oxygen atom or a nitrogen atom, R6, R7 and R8 are each a 1-4C alkyl group, R9 is a 1-8C alkylene group and X is an organic group or an inorganic group). A cosmetic containing it is provided.