Provided is a flame retardant adhesive sheet which is an adhesive sheet having an adhesive agent layer on at least one surface of a substrate, and which is provided with both excellent flame retardant properties and excellent adhesive properties without the adhesive agent layer containing a flame retardant agent. A flame retardant adhesive sheet comprising an adhesive agent layer on at least one surface of a substrate, wherein the substrate has flame retardant properties of VTM-0 in a test according to UL94 standard, the thickness of the adhesive agent layer on one surface is at least 0.6mum and the total thickness of the adhesive agent layer is not more than 2.2mum, and the adhesive agent forming the adhesive agent layer does not contain a flame retardant agent but contains an acrylic copolymer (A) and a specific urethane resin (B).