It is an object of the present invention to provide a culture medium for in vitro culture of a colorectal epithelial stem cell or the like, a method of in vitro culturing a colorectal epithelial stem cell or the like using the culture medium, a prophylactic or therapeutic agent for a bowel disease containing a colorectal epithelial stem cell or the like cultured by the method, a method of administrating, i.e., transplanting a colorectal epithelial stem cell or the like cultured by the method to a bowel disease patient, and a method of isolating a colorectal epithelial stem cell or the like. The culture medium for in vitro culture of a colorectal epithelial stem cell and/or a colorectal epithelial cell characteristically contains serum albumin, Wnt3a, and r-spondin-1.