To provide a metal complex flame retardant capable of enhancing flame-retarding effect without impairing the properties of a synthetic resin, especially, a thermosetting resin compounded therewith, and to provide a resin composition containing the flame retardant.

This metal complex flame retardant consists of a metal complex having, as the ligand, at least one kind selected from the group consisting of furans, thiophenes, pyrroles, imidazoles, oxazoles, thiazoles, pyrans, thiopyrans, bipyridines, oxazines, thiazines, lactams, lactones, and quinolines, and at least one metal atom selected from the group consisting of Be, B, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi and Po. The other objective resin composition containing the metal complex flame retardant is also provided.