The purpose of the present invention is to provide a polyester resin composition for a reflection plate having high reflectance and small decrease of reflectance under exposure to heat during production of an LED package or reflow soldering step for mounting, or exposure to heat and light from a light source. A polyester resin composition of the present invention contains: 30-80% by mass of (A) a polyester resin having a melting point or glass transition temperature of 250° C. or more as measured by DSC; 5-30% by mass of (B) a fibrous reinforcing material having an average fiber length (l) of 2-300 μm, an average fiber diameter (d) of 0.05-18 μm and an aspect ratio (l/d) of 2-20, said aspect ratio being a quotient of 1 by d; and 5-50% by mass of (C) a white pigment (with the total of (A), (B) and (C) being 100% by mass).