The present invention relates to a porcine uroplakin II gene promoter, an expression vector containing the promoter, and a method for producing useful proteins using the vector. The promoter of the present invention promotes the bladder-specific expression of a target protein at high efficiency. An animal, which was transformed using the inventive promoter so as to express the target protein, secretes the target protein in its urine at high concentration, and the protein thus produced shows a superior physiological activity to that of the same kind of the existing protein. As a result, the inventive promoter, the expression vector and transgenic animal using the promoter, can be advantageously used in the production field of useful proteins that are medicinally valuable.