There are provided a novel curable polyester, a cured product thereof, and a process for preparing the same, as well as a resist composition and a jet Printing ink composition comprising the curable polyester, curing methods and uses thereof. The curable polyester of the present invention has a polyester skeleton as a main chain and also has an oxetanyl group at the molecular end. The curable polyester of the present invention is excellent in curability and has excellent flexibility, adhesion and mechanical strength, and also exhibits high safety to the human. The resist composition containing a novel curable polyester having an oxetanyl group at the molecular end of the present invention is suitable for a solder resist for forming a pattern with high accuracy or an interlayer insulation film because neither bleeding after screen printing nor sagging upon heat curing occurs, and the jet printing ink composition containing a novel curable polyester having an oxetanyl group at the molecular end of the present invention is suitable for a solder resist or an interlayer insulation film, which is excellent in line width retention of a thin line pattern because neither bleeding nor sagging upon heat curing occurs.