Provided is a flame retardant adhesive sheet having an adhesive agent layer on at least one surface of a base material, which even when the adhesive agent layer does not contain a flame retardant agent, has both excellent flame retardant properties and adhesive properties. The present invention is concerned with a flame retardant adhesive sheet including an adhesive agent layer on at least one surface of abase material, wherein the base material has flame retardant properties adapted to VTM-0 in a test according to the UL94 standard; a thickness per surface of the adhesive agent layer is 0.6 μm or more, and a total thickness of the adhesive agent layer is not more than 2.2 μm; the adhesive agent constituting the adhesive agent layer does not contain a flame retardant agent but contains (A) an acrylic copolymer and (B) a specified urethane resin.