A producing method of a cellulose polymer powder is provided, which comprises dissolving a cellulose polymer by exposure to an organic solvent containing, as the main component, an ester-based solvent having from 2 to 8 carbon atoms, a ketone-based solvent having from 4 to 10 carbon atoms, or an alcohol-based solvent having from 3 to 6 carbon atoms, and carbon dioxide, and then removing the carbon dioxide and the organic solvent from the solution. A producing method of an organic solvent solution of a cellulose polymer is also provided.