Abstract: The invention pertains to a process for producing oxidized cellulose having a high molecular weight, by pre-treating cellulose in a non-alkaline solvent for cellulose so as to lower its crystallinity, and then oxidizing it using an oxidizing system predominantly oxidizing the 6-hydroxymethyl groups or the 2,3-dihydroxyethylene groups to carbaldehyde and/or carboxyl groups. The oxidizing agent is preferably a nitroxyl compound or periodate, and the product is useful as a water-absorbent.