A toner binder for electrophotography excellent in low temperature fixing properties and anti-hot offset properties comprising styrene (co)polymer(s) (A) comprising a modified styrene (co)polymer modified by unsaturated dicarboxylic acids of C4 to C30, ester-forming derivatives thereof, (meth)acrylic acid, or alkyl (meth)acrylates (alkyl group of C1 to C24); said modified styrene (co)polymer containing constituent units derived from a monomer used in the modification is 0.1 to 9 wt %, and a toner using the toner binder. The (co)polymer(s) (A) includes a species that shows at least one GPC peak each in the regions of the molecular weight of 2,000 to 20,000 and 50,000 to 5 million.