The present invention aims to provide a chlorinated vinyl chloride-based resin composition with excellent thermal stability and a molded body thereof. The present invention relates to a resin composition for molding, including a chlorinated vinyl chloride-based resin, a thermal stabilizer, and a polyalcohol and/or a partial ester of a polyalcohol. The chlorinated vinyl chloride-based resin has a chlorine content of 65% by weight or more and less than 72% by weight. The chlorinated vinyl chloride-based resin has, based on the total number of moles of a structural unit (a) —CCl2—, a structural unit (b) —CHCl—, and a structural unit (c) —CH2—, a proportion of the structural unit (a) of 17.5 mol % or less, a proportion of the structural unit (b) of 46.0 mol % or more, and a proportion of the structural unit (c) of 37.0 mol % or less. The thermal stabilizer contains at least one of a compound represented by the formula Ca1-xZnx (OH)2 where x satisfies the inequality 0