Disclosed are respiratory-deficient yeast except Saccharomyces cerevisiae AH22R⁻ , said respiratory-deficient yeast being transformed with a DNA containing a gene encoding a protein foreign to yeast and a method for preparing a protein foreign to yeast described above, which comprises culturing the yeast, and producing and accumulating the protein in a culture. The respiratory-deficient yeast of the present invention can produce a higher amount of protein than its parent strain.