The present invention provides the amino acid sequence and base sequence of a Pseudonocardia thermophila-derived nitrile hydratase, provides further a method for changing its amino acid sequence and base sequence without substantially changing the functions of said nitrile hydratase, and nitrile hydratases having a base sequence and an amino acid sequence as changed on the basis of said method, and provides furthermore a recombinant plasmid having the gene of said nitrile hydratase, a transformant containing said recombinant plasmid, a method of using said transformant for producing said enzyme, and a method of using said transformant for producing the corresponding amide compound from a nitrile compound.