Provided are: a phosphate amine salt composition which can be used as a flame retardant that is capable of imparting excellent flame retardancy and weather resistance to synthetic resins without a risk of corroding a processing machine; a phosphate amine salt flame retardant composition; a flame-retardant synthetic resin composition containing the same; and a molded article thereof. The phosphate amine salt composition contains at least one phosphate amine salt, and the ammonium cation content therein is 100 to 2,000 ppm by mass. An amine in the phosphate amine salt composition is preferably melamine or piperazine.
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