An adherend surface of an adherend is stuck with a protection sheet being in substantially the same shape as the adherend surface and including base and adhesive layer by a method including: sticking the sheet on a first surface of a sticking tool foldable along a symmetry-axis position of the sheet; folding the tool with the sheet such that a second surface opposite to the first surface comes inside; peeling the sheet to a folded portion of the tool to expose a portion of the adhesive layer with the tool folded; pressing the exposed portion of the adhesive layer against the adherend surface to stick a portion of the sheet on the adherend; and moving the tool along the adherend surface to expose a remaining portion of the adhesive layer and pressing the remaining portion against the adherend surface to stick a remaining portion of the sheet on the adherend.