To provide a polybutylene terephthalate-based resin composition high in laser fusibility and used for laser fusion.

This polybutylene terephthalate-based resin composition for laser fusion comprises a polybutylene terephthalate-based resin (A), a fatty acid-based compound (B) (for example, a 12 to 36C fatty acid ester, or a 12 to 36C fatty acid metal salt), and, if necessary, a cyclic polyester oligomer (C) (for example, a cyclic polyalkylene terephthalate oligomer). The amount of the fatty acid-based compound (B) in the resin composition may usually be about 0.01 to 1.0 pt.wt. per 100 pts.wt. of the polybutylene terephthalate-based resin (A).