A thermally decomposable binder resin containing, as an active ingredient, a rosin derivative (A) that is obtained by subjecting a rosin (a) to distillation and a disproportionation treatment and/or hydrogenation treatment, wherein the rosin derivative (A) has a 99 wt % weight loss temperature of 500° C. or lower in thermogravimetric measurement, under an air atmosphere at a heating rate of 5° C./min, a binder resin composition containing the resin, and a use of the binder resin composition.