A polyester resin toner binder which gives a toner with good anti-blocking property at high temperature and high humidity and good low-temperature fixing ability. The present invention is directed to a toner binder for developing electrostatic charge images, which binder comprises a condensation-polymerization polyester resin, the polyester resin being a product formed in the presence of a catalyst (a) represented by the following general formula (I): Ti(—X)m(—OR)n  (I) wherein R, X, m and n are as defined herein.