The present invention provides a resin composition for injection molding that can provide a molded body having excellent thermal stability, excellent thermal fluidity, and high water pressure resistance without a heavy metal such as lead or tin. The present invention also provides a molded body including the resin composition for injection molding. Provided is a resin composition for injection molding containing: a chlorinated polyvinyl chloride;
polyvinyl chloride; and a thermal stabilizer, the thermal stabilizer containing a calcium alkyl carboxylate and a zinc compound, the polyvinyl chloride having a degree of polymerization of 400 to 1,000, the resin composition containing the polyvinyl chloride in an amount of 1 to 30 parts by mass relative to 100 parts by mass of the chlorinated polyvinyl chloride.