The nanoscale peeling of the graphene sheet is numerically studied by molecular mechanics simulation. In the simulation, a rectangular-shaped monolayer graphene sheet with each side of 38 Å×21 Å, comprised of 310 carbon atoms, is peeled from the rigid graphite surface. The six-membered ring around the center position is lifted. We have first obtained the vertical force-distance curve which reflects the transition of the graphene shape from the surface- to the line-contact during the peeling process. The successive partial peelings of the graphene around the lifting center appear as discrete jumps in the force curve, which induce the arched deformation of the graphene sheet. [DOI: 10.1380/ejssnt.2009.783]