Disclosed is a live bacterium preparation or food containing a lactic acid bacterium comprising a lactic acid bacterium, Lactobacillus salivarius, as an active ingredient. There is provided a live bacterium preparation and food containing a lactic acid bacterium that can prevent onset, recurrence and exacerbation of periodontal disease and/or dental caries caused by periodontopathic bacteria and cariogenic bacteria and can prevent generation of halitosis and maintain pH of saliva at a physiologically normal level by normalizing intraoral microflora.