To provide a resin composition for a window frame excellent in low extension and contraction, heat resistance and weatherability and combining impact resistance and the window frame using it.

This resin composition for a window frame and the window frame is a resin composition comprising a chlorinated vinyl chloride-based resin A post-chlorinating a vinyl chloride-based resin and a resin B, the resin B is one graft-copolymerizing vinyl chloride or a vinyl monomer making a main component of vinyl chloride on an acrylic-based copolymer copolymerizing alkyl (meta)acylate monomer and a multi-functional monomer in which the glass transfer temperature of a single polymer is -100 to -20°C. A molding obtained from the resin composition has the heating extension and contraction of a range of -1.3 to 0% (measured by the method conformed to JIS K6785) or vicat softening temperature of a range of 100-120°C (measured by the method conformed to JIS K7206) and Izod impact value of 50 kgf.cm/cm2 (measured to the method conformed to JIS K7110).