The present invention provides an antibody to human IL-3Rα chain, which does not inhibit IL-3 signaling and binds to B domain of the human IL-3Rα chain but does not bind to C domain of the human IL-3Rα chain a composition for preventing or treating a blood tumor in which a cell expressing IL-3Rα is found in bone marrow or peripheral blood of a subject, which comprises the antibody to human IL-3Rα as an active ingredient and a method for treating a blood tumor in which a cell expressing IL-3Rα is found in bone marrow or peripheral blood, which comprises administering, to a subject, a composition comprising the IL-3Rα antibody as an active ingredient.
