Disclosed are: a novel therapeutic agent for cancer such as esophageal squamous cell carcinoma； a method for determining the prognosis of caner； and a method for detecting cancer such as esophageal squamous cell carcinoma or determining the prognosis of the cancer using a sample that can be collected non-invasively. The therapeutic agent for cancer comprises an antibody capable of performing an antigen-antibody reaction with FGFRL1 to inhibit the proliferation of cancer cells or an antigen-binding fragment thereof as an active ingredient. The method for determining the prognosis of cancer comprises determining the amount of expressed FGFRL1 in a cancer tissue separated from a living body, wherein it is determined that the prognosis is bad when the amount of expressed FGFRL1 is large. The method for detecting cancer comprises measuring FGFRL1 or a fragment thereof extracted from a biological tissue or FGFRL1 or a fragment thereof in blood separated from a living body, wherein it is determined that cancer is developed when the concentration of FGFRL1 or the fragment thereof is higher than that in a tissue or blood from a normal person.
