To provide a stock paper requiring counterfeit-prevention such as paper money and various documents, and further, in a papermaking machine, to provide multi-layered paper having both surface window-opening parts obtained by removing an upper layer and lower layer of a part of the multi-layer combined paper made into three or more layers of the upper layer, a middle layer and the lower layer, for forming the window-opening parts to expose the middle layer.

The stock paper formed of at least three layers of the upper paper layer 1, middle paper layer 2, and lower paper layer 3 has a transparent part 6 having transparency or translucency formed in at the middle layer 2. The multi-layer paper 4 having a transparent window 8 formed with window-opening parts 5, 7 in the upper paper layer 1 and lower paper layer 3 respectively by removing the paper layers at the same region with the transparent part 6.