A method for efficiently manufacturing a first polypeptide fragment having cysteine at the N-terminal and a second polypeptide fragment having the C-terminal modified which are suitable for the NCL method, comprising: A step of reacting a polypeptide having the following structure: (N-terminal) second polypeptide fragment-Cys-W-(His)n-Z-Met-first polypeptide fragment (C-terminal) [wherein n means an integer from 0 - 10, Cys is cysteine, W means any 1, 2, or 3 amino acids, Z means any 0, 1, or 2 amino acids, His means histidine, Met means methionine, and the N-terminal of the first polypeptide fragment is cysteine] with CNBr to obtain the following polypeptide fragments: a first polypeptide fragment having cysteine at the N-terminal and a third polypeptide fragment having the following structure: (N-terminal) second polypeptide fragment-Cys-W-(His)n-Z-Met' (C-terminal) [wherein Met' means a Met derivative]; A step of reacting said third polypeptide fragment with a compound represented by the following formula: [wherein X is a sulfur atom or an oxygen atom, and R 1 and R 2 are leaving groups] and subsequently, in an organic solvent, reacting with a compound represented by the following formula: [wherein Y is an oxygen atom, a sulfur atom, or =NH, and R 3 is a hydrogen atom, an acyl group, or an alkoxycarbonyl group] to obtain a second polypeptide fragment having the C-terminal modified having the following structure: (N-terminal) second polypeptide fragment-C(=O)-NH-C(=Y)NHR 3 (C-terminal). A step of reacting a polypeptide having the following structure: (N-terminal) second polypeptide fragment-Cys-W-(His)n-Z-Met-first polypeptide fragment (C-terminal) [wherein n means an integer from 0 - 10, Cys is cysteine, W means any 1, 2, or 3 amino acids, Z means any 0, 1, or 2 amino acids, His means histidine, Met means methionine, and the N-terminal of the first polypeptide fragment is cysteine] with CNBr to obtain the following polypeptide fragments: a first polypeptide fragment having cysteine at the N-terminal and a third polypeptide fragment having the following structure: (N-terminal) second polypeptide fragment-Cys-W-(His)n-Z-Met' (C-terminal) [wherein Met' means a Met derivative]; a first polypeptide fragment having cysteine at the N-terminal and a third polypeptide fragment having the following structure: (N-terminal) second polypeptide fragment-Cys-W-(His)n-Z-Met' (C-terminal) [wherein Met' means a Met derivative]; A step of reacting said third polypeptide fragment with a compound represented by the following formula: [wherein X is a sulfur atom or an oxygen atom, and R 1 and R 2 are leaving groups] and subsequently, in an organic solvent, reacting with a compound represented by the following formula: [wherein Y is an oxygen atom, a sulfur atom, or =NH, and R 3 is a hydrogen atom, an acyl group, or an alkoxycarbonyl group] to obtain a second polypeptide fragment having the C-terminal modified having the following structure: (N-terminal) second polypeptide fragment-C(=O)-NH-C(=Y)NHR 3 (C-terminal). X is a sulfur atom or an oxygen atom, and R 1 and R 2 are leaving groups] Y is an oxygen atom, a sulfur atom, or =NH, and R 3 is a hydrogen atom, an acyl group, or an alkoxycarbonyl group]