PROBLEM TO BE SOLVED: To provide a composition for an oral cavity that exhibits an excellent bactericidal action against a bacterium in a state of forming a biofilm in the oral cavity.SOLUTION: The composition for an oral cavity remarkably exerts the bactericidal action against the bacterium forming a biofilm in the oral cavity by synergistic actions of selecting cetylpyridinium chloride as a bactericide and integrally and indivisibly combining the cetylpyridinium chloride with cinnamon or an extract thereof.