PURPOSE: To provide the title resin composition capable of affording film condensers of small temperature-dependency in its dielectric loss and capacity, also of high breakdown voltage, comprising a polybutadiene resin, a crosslinkable monomer, and a curing agent.

CONSTITUTION: The objective composition comprising (1) 30W70 parts by wt. of a polybutadiene resin, (2) 30W70 parts by wt. of a crosslinkable monomer and (3) 0.5W3.0 parts by wt. of a curing agent. This composition has low dielectric loss and dielectric constant, furthermore with their low temperature-dependency. Said polybutadiene resin is, e.g. polybutadiene homopolymer, a modified polybutadiene, etc., consisting of at least 90 mole % of 1,2-polybutadiene chain, with a molecular weight of 1000W5000. As the crosslinkable monomer, is used, e.g. styrenecor its devivative), divinylbenzene, diallyl(iso)phthalate, etc. The curing accelerator to be applied, is, e.g. a metal solt of octenoic acid, of naphthenic acid, etc. This composition has potential of giving film condensers of easy film formability and of high dimensional accuracy.