Abstract: The present invention relates to a composition for inhibiting biofilm comprising at least one selected from the group consisting of Lactobacillus rhamnosus, its culture medium, its extract and its cell-free supernatant and collagen hydrolysate. Although Lactobacillus rhamnosus can inhibit biofilm formation even as a single agent, the inhibitory ability is significantly increased when it is simultaneously treated with the collagen hydrolysate. The collagen hydrolysate inhibits acid production of Lactobacillus rhamnosus or Streptococcus mutans. Thus, the Lactobacillus rhamnosus and collagen hydrolysate can be usefully used as a composition for inhibiting the production of biofilms, in particular biofilms occurring in the oral cavity and a composition for preventing, alleviating, or treating oral diseases caused by the biofilms.