PROBLEM TO BE SOLVED: To provide a preventive and treating agent of stress bowel disorder of diarrhea-type.SOLUTION: Provided are a new cryotolerant strain Lactobacillus gasseri CP2305s (NITE BP-1405), or cryotolerant strains derived from Lactobacillus gasseri CP2305 (FERM BP-11331) or Lactobacillus gasseri CP2305s (NITE BP-1405), and a preparation method thereof. Also provided is a stress bowel disorder-alleviating agent containing cells and/or processed cells of the cryotolerant strain as the effective component. Also provided are food additives, animal feed additives, animal feeds and pharmaceutical compositions containing the alleviating agent.