The present invention has an object to provide a tumor necrosis factor mutant protein, particularly, a tumor necrosis factor mutant protein specific to TNF-R1 or TNF-R2; tumor necrosis factor inhibitor; or tumor necrosis factor preparation containing it as an effective ingredient, and the object is solved by providing a tumor necrosis factor mutant protein where one or more amino acid residues selected from the group consisting of 29th, 31st, 32nd, 145th, 146th and 147th, or the group consisting of 84th to 89th from the N-terminal of the amino acid sequence of SEQ ID NO:1 is/are replaced with other amino acid residue(s); a tumor necrosis factor inhibitor; and a tumor necrosis factor preparation containing it as an effective ingredient.