A flame-retardant biaxially oriented polyester film is obtained by imparting flame retardancy to a polyester film itself using a phosphorus flame retardant, a flame-retardant polyester film laminate is formed from the same, and a flexible circuit board is provided. The present invention is obtained from a flame-retardant biaxially oriented polyester film which contains, based on the weight of the polyester film, 70 to 99.5% by weight of polyethylene terephthalate or polyethylene naphthalate, and 0.5 to 30% by weight of flame retardant particles having an average particle diameter of 0.5 to 3.0 μm and being represented by a specific phosphinate or diphosphinate, wherein the number of coarse particles having a maximum length of 10 μm or more contained in the polyester film is 10/m2 or less.