The present invention provides an anti-fouling pressure-sensitive adhesive sheet and anti-fouling treatment method capable of preventing peeling from overlapping portions when adjacent anti-fouling pressure-sensitive adhesive sheets are attached by allowing end portions thereof to overlap each other. The anti-fouling pressure-sensitive adhesive sheet of the present invention includes a base material layer; a pressure-sensitive adhesive layer provided on one side of the base material layer; and an anti-fouling layer provided on another side of the base material layer, wherein the anti-fouling pressure-sensitive adhesive sheet has, at an end portion thereof, a bonding margin including parts of the base material layer and the pressure-sensitive adhesive layer, the parts extending beyond the anti-fouling layer.