The present invention provides a reinforced polyester resin composition, which comprises, with respect to 100 parts by mass of a polyester resin, 0.01 to 400 parts by mass of an inorganic filler as component (A) and 0.001 to 10 parts by mass of a metal salt of a sulfonamide compound as component (B), the metal salt of the sulfonamide compound having a structure represented by Formula (1): wherein R1 and R2 independently represent a hydrogen atom or the like; R1 and R2 are also optionally linked together to form a cyclic group; n represents number of 1 or 2; when n is 1, M represents an alkali metal atom or the like; when n is 2, the plural R1s and R2s are each optionally different; M represents a divalent metal atom or linking group; and when M is the linking group, either of R1 and R2 is an alkali metal.