A flame retardant includes magnesium-hydroxide particles that contain at least one transitional metal compound. The at least one transitional metal compound is at least one compound selected from a group consisting of copper compound, cobalt compound, nickel compound, zinc compound and titanium compound. The at least one transitional metal compound is contained in the magnesium-hydroxide particles with the content of 100 to 1000 mass ppm in terms of metals. In addition, the total content of the copper compound, the cobalt compound and the nickel compound is 1000 mass ppm in terms of metals or less while the total content of the zinc compound and the titanium compound is 1000 mass ppm or less.