Flame retardant adhesive sheet

A flame retardant adhesive sheet comprising an adhesive agent layer on at least one surface of a base material, wherein

• the base material has flame retardant properties adapted to VTM-0 in a test according to the UL94 standard;
• a thickness of the adhesive agent layer disposed on at least one surface of the base material 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 comprise a flame retardant agent but comprises (A) an acrylic copolymer and (B) a urethane resin;
• and
• the urethane resin (B) is a urethane resin which is obtained by allowing an isocyanate-terminated urethane prepolymer obtained by a reaction between (b1) a polyol and (b2) a polyvalent isocyanate compound to react with (b3) a chain extender, the chain extender (b3) comprising (b4) a compound having two hydroxyl groups and/or amino groups and (b5) a compound having three or more hydroxyl groups and/or amino groups, and the component (b4) and the component (b5) being allowed to react with each other in a proportion of from 70/30 to 100/0 in terms of a mass ratio.