A pulp production process can produce pulp at high yield without using sodium sulfide and high-temperature/high-pressure conditions if compared with the Kraft process and also collect lignin. Pulp is produced by processing wood chips for hydrophlicization at room temperature, using a dilute caustic soda aqueous solution, selectively partially modifying lignin in dilute nitric acid and digesting the wood chips by means of a dilute caustic soda aqueous solution under the atmospheric pressure. Lignin is agglomerated and sorted out from the isolated black liquor.