A novel therapeutic and prophylactic agent for inflammatory bowel diseases and a method for treating inflammatory bowel diseases. The agent comprises a 2-amino-1,3-propanediol derivative ( e.g ., 2-amino-2-[4-(3-benzyloxyphenylthio)-2-chlorophenyl]ethyl-1,3-propanediol hydrochloride) represented by the chemical formula (1) or a pharmaceutically acceptable salt or hydrate thereof: The agent is useful in the treatment or prevention of Crohn's disease, Crohn's disease in large intestine, intestinal Behcet's disease, ulcerative colitis, bleeding rectal ulcer and pouchitis.提供新的發炎性腸道疾病之治療劑或預防劑或其治療方法。發現以如化學式(1)所示之神經胺醇－1－磷酸受體致效劑之2－胺基－1,3－丙二醇衍生物(具體例：2－胺基－2－[4－(3－苄氧基苯硫基)－2－氯苯基]乙基－1,3－丙二醇之鹽酸鹽)，或藥學所容許之其鹽類及水合物作為發炎性腸道疾病，庫隆氏病、大腸庫隆氏病、腸道型貝切多病(ehcet’s disease)、潰瘍性大腸炎、出血性直腸潰瘍或回腸囊炎之治療劑或預防劑為有效的。
