A process for patterning a nanocarbon material includes a step of forming a nanocarbon layer on a substrate; a step of forming a first metal layer on the nanocarbon layer to pattern the first metal layer, the first metal layer containing at least one selected from the group consisting of zinc, tin, indium, aluminum, and titanium; and a step of etching the nanocarbon layer with oxygen plasma using the first metal layer as a positive pattern. Also, a method for manufacturing a semiconductor device including a semiconductor layer containing a nanocarbon material includes a step of patterning a nanocarbon material by the above process; and, a semiconductor device containing a nanocarbon material includes a semiconductor layer including a nanocarbon sub-layer patterned by the process.