PROBLEM TO BE SOLVED: To provide a flame-retardant heat-conductive adhesive sheet having excellent heat conductivity and flame retardancy.SOLUTION: A flame-retardant heat-conductive adhesive sheet 11 has a base material 2 and a flame-retardant heat-conductive adhesive layer 3 provided on at least one surface of the base material 2. In the flame-retardant heat-conductive adhesive sheet 11, the base material 2 comprises a polyester film, the ratio of the thickness of the base material 2 to the overall thickness of the flame-retardant heat-conductive adhesive sheet 11 is less than 0.2, and the heat resistance is not greater than 10 cmK/W.