The present invention provides a mutated histidine decarboxylase suitable for a practical use. Specifically, the present invention provides a mutated histidine decarboxylase having at least one amino acid residue mutated as compared to a wild-type histidine decarboxylase, and having higher histidine decarboxylase activity and/or stability than the wild-type histidine decarboxylase, and also a use thereof. The mutated histidine decarboxylase has Motifs (1) to (6), and an amino acid residue in at least one motif thereof can be mutated. The mutated histidine decarboxylase can also have a mutation of at least one amino acid residue in an amino acid sequence designated by SEQ ID NO: 3 and in a homologous sequence thereto.