According to the present invention, there can be obtained a pressure sensitive adhesive sheet having an adhesive layer which even when the thickness is reduced to 5 μm or less, exhibits a desired adhesive strength. The pressure sensitive adhesive sheet includes a base material having an adhesive layer provided on at least one surface thereof, wherein a pressure sensitive adhesive constituting the adhesive layer contains (A) an acrylic copolymer having a crosslinkable functional group and (B) a urethane resin, the urethane resin is a product obtained by allowing an isocyanate-terminated urethane prepolymer obtained by a reaction between [b1] a diol and [b2] a polyvalent isocyanate compound to react with [b3] a chain extender, and the chain extender is composed of [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, in a proportion of [b4] to [b5] of from 7/3 to 10/0 in terms of a mass ratio.