A method for producing cellulose nanofibers comprising the following steps: oxidizing a cellulosic starting material in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides and mixtures thereof, using an oxidizing agent; and forming the oxidized cellulosic starting material obtained in the step A into nanofibers by preparing a dispersion liquid comprising the oxidized cellulosic starting material and defibrating the starting material while dispersing the starting material in a dispersion medium, and the method either: (i) further comprising the following step: performing a treatment under alkaline conditions, wherein the step C is at least one of the following steps: (C-1) treating the cellulosic starting material in water having a hydroxide ion concentration of 0.75 to 3.75 mol/L before the step A; and (C-2) subjecting the oxidized cellulosic starting material obtained in the step A to hydrolysis in an alkaline solution having a pH between 8 and 14 after the step A and before the step B, wherein an oxidizing agent or a reducing agent is added to the alkaline solution and the oxidizing agent is selected from oxygen, hydrogen peroxide, hypochlorite or a combination of two or more thereof, and wherein ozone is not used in combination with the oxidising agent; or (ii) further comprising the following step: performing a treatment under alkaline conditions, wherein the step C comprises both of the following steps: (C-1) treating the cellulosic starting material in water having a hydroxide ion concentration of 0.75 to 3.75 mol/L before the step A; and (C-2) subjecting the oxidized cellulosic starting material obtained in the step A to hydrolysis in an alkaline solution having a pH between 8 and 14 after the step A and before the step B oxidizing a cellulosic starting material in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides and mixtures thereof, using an oxidizing agent; and forming the oxidized cellulosic starting material obtained in the step A into nanofibers by preparing a dispersion liquid comprising the oxidized cellulosic starting material and defibrating the starting material while dispersing the starting material in a dispersion medium, and the method either: (i) further comprising the following step: performing a treatment under alkaline conditions, wherein the step C is at least one of the following steps: (C-1) treating the cellulosic starting material in water having a hydroxide ion concentration of 0.75 to 3.75 mol/L before the step A; and (C-2) subjecting the oxidized cellulosic starting material obtained in the step A to hydrolysis in an alkaline solution having a pH between 8 and 14 after the step A and before the step B, wherein an oxidizing agent or a reducing agent is added to the alkaline solution and the oxidizing agent is selected from oxygen, hydrogen peroxide, hypochlorite or a combination of two or more thereof, and wherein ozone is not used in combination with the oxidising agent; or (ii) further comprising the following step: performing a treatment under alkaline conditions, wherein the step C comprises both of the following steps: (C-1) treating the cellulosic starting material in water having a hydroxide ion concentration of 0.75 to 3.75 mol/L before the step A; and (C-2) subjecting the oxidized cellulosic starting material obtained in the step A to hydrolysis in an alkaline solution having a pH between 8 and 14 after the step A and before the step B (i) further comprising the following step: performing a treatment under alkaline conditions, wherein the step C is at least one of the following steps: (C-1) treating the cellulosic starting material in water having a hydroxide ion concentration of 0.75 to 3.75 mol/L before the step A; and (C-2) subjecting the oxidized cellulosic starting material obtained in the step A to hydrolysis in an alkaline solution having a pH between 8 and 14 after the step A and before the step B, wherein an oxidizing agent or a reducing agent is added to the alkaline solution and the oxidizing agent is selected from oxygen, hydrogen peroxide, hypochlorite or a combination of two or more thereof, and wherein ozone is not used in combination with the oxidising agent; (C-1) treating the cellulosic starting material in water having a hydroxide ion concentration of 0.75 to 3.75 mol/L before the step A; and (C-2) subjecting the oxidized cellulosic starting material obtained in the step A to hydrolysis in an alkaline solution having a pH between 8 and 14 after the step A and before the step B, wherein an oxidizing agent or a reducing agent is added to the alkaline solution and the oxidizing agent is selected from oxygen, hydrogen peroxide, hypochlorite or a combination of two or more thereof, and wherein ozone is not used in combination with the oxidising agent; or (ii) further comprising the following step: performing a treatment under alkaline conditions, wherein the step C comprises both of the following steps: (C-1) treating the cellulosic starting material in water having a hydroxide ion concentration of 0.75 to 3.75 mol/L before the step A; and (C-2) subjecting the oxidized cellulosic starting material obtained in the step A to hydrolysis in an alkaline solution having a pH between 8 and 14 after the step A and before the step B (C-1) treating the cellulosic starting material in water having a hydroxide ion concentration of 0.75 to 3.75 mol/L before the step A; and (C-2) subjecting the oxidized cellulosic starting material obtained in the step A to hydrolysis in an alkaline solution having a pH between 8 and 14 after the step A and before the step B