[Problems] The present invention is to provide a method of solubilizing a carbon nanomaterial, in which a carbon nanomaterial can be dissolved in a hydrophilic solvent easily and uniformly without structural deterioration of the carbon nanomaterial, the dispersibility can be maintained for a prolonged period of time, the solubilizing treatment can be performed at low cost, and the treatment can be easily controlled.[Means for Resolution] The method of solubilizing a carbon nanomaterial of the invention is characterized by mixing a carbon nanomaterial in a hydrophilic solvent, and performing streamer discharge in the hydrophilic solvent to dissolve the carbon nanomaterial in the hydrophilic solvent with the dispersed state thereof maintained stably.