Disclosed is a heat-fusible electrostatic image developing toner which has an excellent balance between fixability at low temperatures and grindability and is excellent in glossiness after fixing. Also disclosed is a resin for toners. A polyester resin for toners which is obtained by polycondensing a polyol component and a polycarboxylic acid component is characterized by containing 20-100 weight % of one or more polyester resins (A1) having a storage elastic modulus from 2.5 x 103 Pa to 5 x 106 Pa at 150° C. wherein the molar average cohesive energy of the polyol component is between 7.0 x 104 and 1.4 x 105 J.