A film-forming agent for cosmetics, which can form a film having excellent water resistance and excellent sebum resistance while also having high washability is provided. Also provided is a cosmetic containing this film-forming agent. The film-forming agent comprises a copolymer polymerized from a monomer composition. The monomer composition comprises: (A) an unsaturated monomer having at least one polysiloxane structure in the molecule； and (B) an unsaturated monomer having at least one acidic group or salt thereof in the molecule； wherein monomer (A) is present in an amount of at least 30 wt % relative to the weight of the monomer composition.
