Flame-retardant composition and flame-retardant synthetic resin composition

A flame retardant composition comprising 20 to 50 parts by mass of component (A), 50 to 80 parts by mass of component (B) (with the proviso that the total of component (A) and component (B) is 100 parts by mass), 0.01 to 5.0 parts by mass of component (C), and 0.01 to 1.0 part by mass of component (D):

• component (A):
• at least one melamine salt selected from the group consisting of melamine orthophosphate, melamine pyrophosphate, and melamine polyphosphate;
• component (B):
• at least one piperazine salt selected from the group consisting of piperazine orthophosphate, piperazine pyrophosphate, and piperazine polyphosphate;
• component (C):
• a silane coupling agent;
• and
• component (D):
• an aliphatic dicarboxylic acid ether ester compound represented by general formula (1) below:
• wherein n represents an integer from 2 to 6, m represents an integer from 1 to 3, and Rl represents a C1-6 alkyl group.