PURPOSE: To easily perform the early diagnosis of human cancer by using a bacterial specimen in human feces.

CONSTITUTION: A bacterial specimen in human feces selected from Escherichia coli and streptococcus faecalis is cultured in vitro in a standard cancer cell culture liquid containing a definite number of cells for a period to enable the sufficient interaction between the bacterial specimen and the standard culture liquid of the cancer cell to be detected. After the cultivation, the number of cancer cells subjected to interaction and the number of non-interacted cancer cells are counted to diagnose the cancer. The extent of the interaction between the test bacteria and the standard cancer cell liquid is defined preferably by comparing with the extent of interaction between the standard cancer cell liquid and a contrast group consisting of bacteria cultured under the same condition. The bacterial strain to be used as the contrast group is selected from E.coli A.T.C.C.55373, E.coli A.T.C.C.55374, E.coli A.T.C.C.55375 and Streptococcus faecalis A.T.C.C.55376.