To provide a novel lactic acid bacterium strain having a broad antibacterial spectrum against bacteria that cause oral diseases, from which a fermented product having good flavor and being excellent in palatability can be produced, and a prophylactic, ameliorating or therapeutic agent for oral diseases using the same. A prophylactic, ameliorating or therapeutic agent for an oral disease, which contains a lactic acid bacterial cell of one or more kinds selected from the group consisting of Lactobacillus rhamnosus strain KO3, Lactobacillus casei strain YU3 and Lactobacillus paracasei strain YU4 or a culture of the cell, or an extract thereof, as an active ingredient.
