A laser-weldable flame-retardant resin composition (for a member located in a transmitting side) comprises (A) a polyester-series resin and (B) at least one phosphinic acid compound selected from the group consisting of a salt of a phosphinic acid, a salt of a diphosphinic acid, and a polymer thereof (preferably, a metal salt). The resin composition may have a laser light transmittance of not less than 15% for a molded product comprising the resin composition and having a thickness of 2 mm. The resin composition may further contain a fluorine-containing resin, a nitrogen-containing flame retardant (e.g., a salt of a triazine compound with cyanuric acid and/or isocyanuric acid), and/or a filler (e.g., a glass fiber), and others. Such a resin composition realizes both of laser-weldability (laser transmissivity) and flame retardancy at high levels.