There is provided a lactic acid bacteria capable of producing a large amount of lactotripeptide; also a fermented milk product that contains a large amount of active ingredient having hypotensive activity and anti-stress effect and can be taken pleasantly, is provided. More specifically, the present invention relates to Lactobacillus helveticus, that is, Lactobacillus helveticus CM4 strain (deposited at National Institute of Bioscience and Human-Technology Agency of Industrial Science and Technology, deposition number FERM BP-6060), characterized in having specific bacteriological properties, the bacteria, when cultured in a medium of animal milk containing 9 wt % solid of non-fat milk, producing tripeptides Val-Pro-Pro and Ile-Pro-Pro in an amount of 60 mu g in terms of Val-Pro-Pro per ml medium, and the bacteria exhibiting extracellular proteinase activity of not lower than 400U / OD590. The present invention also relates to a fermented milk product obtained by fermenting an animal milk with these lactic acid bacteria.