The present invention provides a non-halogen-based flame retardant composition and flame retardant resin composition wherein a small amount of addition achieves an excellent flame retardancy, an amount of elution of a flame retardant from the thermoplastic resin is extremely small even under high temperature and high humidity, and it has water-resistant property. A phosphate ester amide compound of general formula (I), a nitrogen-containing compound having a 1,3,5-triazine structure or 1,3,5-triazine fused ring structure, and optionally, a metal oxide or metal salt are used together. Further optionally, a dripping inhibitor is blended. wherein, R1, R2, R3 and R4 are each independently hydrogen or C1-3 alkyl, R11, R12, R13 and R14 are each independently C1-3 alkylene, R15 is C1-6 alkylene, and R5 and R6 are each independently hydrogen or C1-6 alkyl.