The present invention provides a method for producing fermented milk, the method employing a lactic acid bacterium capable of improving proliferative properties of Bifidobacterium, and a fermented milk prepared by the production method. Specifically, the present invention provides a method for producing a fermented milk, including fermenting a fermentation base using both Lactococcus lactis strain having cell wall-enveloped proteinase, PrtP, and bacteria belonging to a genus Bifidobacterium, and a fermented milk prepared by the production method.