To provide a copolymer latex having excellent stickiness and adhesive strength of a latex film.

The copolymer latex uses a specific alkyl mercaptan with respect to 100 parts weight of the monomer, when the monomer, comprising 1-20 wt.% of an alpha-methylstyrene monomer, 30-70 wt.% of an aliphatic conjugated diene monomer, 0.5-10 wt.% of an ethylene-based unsaturated carboxylic acid monomer, and 0-68.5 wt.% of another monomer to be copolymerized with these monomers (the total of the monomers is 100 wt.%), is subjected to emulsion polymerization. Addition of total of the alpha-methylstyrene monomer used in the polymerization is completed before 60 wt.% of the total monomer of 100 wt.% is added.