NOVELTY - A resin composition comprises graft copolymer which contains rubber-like polymer with refractive indexes of 1.51-1.54 and copolymer containing aromatic vinyl compound and unsaturated nitrile compound which are grafted onto rubber-like polymer as polymer unit, unsaturated nitrile type copolymer which contains aromatic vinyl compound and unsaturated nitrile compound as polymer unit, and heat-resistant acrylic resin.    USE - A resin composition for optical film, polarizing plate protective film and retardation film used for polarizing plate (claimed) for LCD (e.g. in-plane switching (IPS) mode LCD e.g. TV, personal computer, mobile telephone, car navigation, medical device and industrial apparatus), plasma display, organic electroluminescent display, field emission display and display of rear projection TV. Can also be used for optical element (e.g. waveguide in transparent substrate field), optical medium, front surface board of display, display substrate, touch panel, solar cell, other optical communication systems and optical exchange systems, optical measuring system, lens, optical fiber, optical fiber coating material, lens of LED, lens cover, and liquid crystal optical compensation films and viewing angle control film for quarter wavelength plate and one half wavelength plate.    ADVANTAGE - The resin composition provides optical film which is excellent in transparency, heat resistance and mechanical characteristic, has small absolute value of photoelastic coefficient and shows negative birefringence.    DETAILED DESCRIPTION - A resin composition comprises graft copolymer which contains rubber-like polymer with refractive indexes of 1.51-1.54 and copolymer containing aromatic vinyl compound and unsaturated nitrile compound which are grafted onto rubber-like polymer as polymer unit, unsaturated nitrile type copolymer which contains aromatic vinyl compound and unsaturated nitrile compound as polymer unit, and heat-resistant acrylic resin. The composition provides optical film which has glass transition temperature of greater than or equal to 110 degrees C and haze of film of 50 mu m-thick measured based on JIS K7136 of less than or equal to 2. An INDEPENDENT CLAIM is included for a polarizing plate comprising protective film as retardation film obtained by other molding process of resin composition which contains acrylic resin and does not contain styrene resin which is bonded together on both surfaces of polarizing film.