A flame retardant containing an aromatic phosphoric acid ester represented by the general formula (I): wherein R1 to R4, R7, and R8 each independently represent a C1-4 alkyl group or a C1-4 alkoxy group; R5, R6, and R9 each independently represent a C1-10 alkyl group or a C1-10 alkoxy group; n represents an integer of 1 to 10; n1 and n2 each independently represent an integer of 0 to 3; m1 and m2 each independently represent an integer of 0 to 4; p represents an integer of 0 to 26; and k represents an integer of 1 to 12; and when p is 2 or more, any two substituents R9 may be bonded to each other, and may be bonded to a carbon atom(s) of a ring to which the above substituents R9 are bonded, forming another ring.