The present invention relates to a method for producing a fermented milk, including: performing fermentation using both bacteria belonging to the genus Bifidobacterium and bacteria belonging to the genus Lactococcus as lactic acid bacteria, wherein the bacteria belonging to the genus Lactococcus have the following bacteriological properties: (1) fermentability which curdles a 10% (W/W) reconstituted skim milk medium when cultivated at a temperature of 25°C to 37°C for 16 hours； (2) Bifidobacterium longum growth-promoting properties which lead to a viable count of Bifidobacterium longum of 5 ×10 8 CFU/g or more, when co-cultivated with Bifidobacterium longum in the 10% (W/W) reconstituted skim milk medium until the pH thereof is 4.4 to 4.6； and (3) Bifidobacterium longum survivability-improving properties during storage, which lead to a survival rate of Bifidobacterium longum of 30% or more, after co-cultivation with Bifidobacterium longum in the 10% (W/W) reconstituted skim milk medium until the pH thereof is 4.4 to 4.6, rapid cooling, and two weeks storage at 10°C, and also relates to a fermented milk prepared by the production method.
