To provide a CD44 positive TMEM-180(Transmembrane protein-180) positive blood floating particle, a method for selecting a cancer patient that can be effectively treated by anti-TMEM-180 antibody therapy using the same, an anticancer agent containing the anti-TMEM-180 antibody for the selected patient, and a kit for use in the method.SOLUTION : The present invention provides (1) an isolated TMEM-180 positive CD44 positive extracellular vesicle, (2) a method for analyzing the effectiveness of therapy of an anticancer agent containing an anti-TMEM-180 antibody to determine the presence or absence of a CD44 positive TMEM-180 positive cancer cell, and a kit for use in the method.SELECTED DRAWING : None