The invention provides a flame retardant composition comprising 1-99 weight parts of a salt of piperazine and an inorganic compound selected from among piperazine phosphate, piperazine pyrophosphate and piperazine polyphosphate, or a mixture of two or more of these piperazine salts (ingredient (A)), 99-1 weight parts of a salt of melamine and an inorganic compound selected from among melamine phosphate, melamine pyrophosphate and melamine polyphosphate, or a mixture of two or more of these melamine salts (ingredient (B)) (wherein, the sum of ingredient (A) and ingredient (B) is 100 weight parts), 0-50 weight parts of an arbitrary ingredient (ingredient (C)), and 0.01-20 weight parts of a silicone oil having a viscosity at 25.degree. C. of 5000 mm.sup.2/s (ingredient (D)) which is added thereto. This flame retardant not only has superior flame retarding properties, but also has enhanced powder properties and anti-hygroscopic properties, and when it is added to a resin, there is little change of electrical resistance.