A thrombin mutant in which at least serine at position 205 among amino acids in the active center of the thrombin B chain has been replaced with another amino acid, and further at least one of the following replacements have been introduced: (I) replacement of arginine at position 89 in the B-chain with another amino acid (II) replacement of threonine at position 69 or serine at position 22 in the B-chain with another amino acid (III) replacement of alanine at position 200 in the B-chain with another amino acid and (IV) replacement of lysine at position 65 in the B-chain with threonine.
