Disclosed are a method for detecting liver cancer capable of detecting liver cancer with high specificity and a diagnostic therefor, as well as a novel therapeutic drug for cancer having an excellent anticancer effect. The method for detecting liver cancer cells in a sample utilizes as an index the expression of dlk gene. The expression of dlk gene may be measured by immunoassay using an anti-dlk antibody or by measuring mRNA of dlk gene. The therapeutic drug for cancer comprises as an effective ingredient an antibody which undergoes antigen-antibody reaction with Dlk expressing on surfaces of cancer cells and which exerts anticancer action against the cancer cells.
