Flame retardant synthetic leather having high flame retardancy and excellent physical properties (light resistance, heat resistance and feeling). The flame retardant synthetic leather contains an organic phosphorus compound (component A) represented by the following formula (1). (In the formula, X 1 and X 2 are the same or different and each an aromatic substituted alkyl group represented by the following formula (2).) €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ(5AL)5(5Ar) n €ƒ€ƒ€ƒ€ƒ€ƒ(2) (In the formula, AL is a branched or linear aliphatic hydrocarbon group having 1 to 5 carbon atoms, and Ar is a phenyl group, naphthyl group or anthryl group, all of which may have a substituent. "n" is an integer of 1 to 3, and Ar may be bonded to any carbon atom contained in AL.)