A carbon nanosheet, which is a sheet-form carbon nanomaterial having a larger area as compared with that of a similar conventional product and a side length of about 1 μm, and a method for producing the carbon nanosheet. The carbon nanosheet production method includes a step of mixing a solution of an iron atom-containing compound dispersed in a solvent with an alcohol, to thereby prepare a solution mixture; and a step of irradiating the solution mixture with plasma, to thereby produce a carbon nanosheet. The carbon nanosheet has a side length of 0.5 μm to 2.5 μm.