A method for acquiring information on an analyte, comprising the steps of: bringing a polypeptide that is the analyte into contact with a capture substance that binds to the polypeptide to form a complex comprising the polypeptide and the capture substance; bonding the capture substance in the complex to a first solid phase to immobilize the complex onto the first solid phase; collecting the first solid phase having the complex immobilized on the first solid phase; releasing the complex from the collected first solid phase, and then bonding the capture substance in the released complex to a second solid phase to immobilize the complex onto the second solid phase; and acquiring information on the polypeptide from the complex immobilized on the second solid phase, wherein the capture substance that binds to at least one of the first solid phase and the second solid phase binds to a C-terminal region of the polypeptide and is a H31L21 antibody, wherein the capture substance comprises a first capture substance having a first bonding substance and a second capture substance having a second bonding substance, and at least one of the first capture substance and the second capture substance binds to a C-terminal region of the polypeptide; the first solid phase has a first bonding partner that bonds specifically to the first bonding substance and the second solid phase has a second bonding partner that bonds specifically to the second bonding substance; in the step of immobilizing the complex onto the first solid phase, the complex is immobilized onto the first solid phase through a specific bonding between the first bonding substance and the first bonding partner; and in the step of immobilizing the complex onto the second solid phase, the complex is immobilized onto the second solid phase through a specific bonding between the second bonding substance and the second bonding partner, wherein the polypeptide is further brought into contact with a substance for detection which has a labeling substance and binds to the polypeptide to form a complex comprising the polypeptide, the capture substance and the substance for detection, wherein the substance for detection binds to a N-terminal region of the polypeptide, and wherein the polypeptide is amyloid β. bringing a polypeptide that is the analyte into contact with a capture substance that binds to the polypeptide to form a complex comprising the polypeptide and the capture substance; bonding the capture substance in the complex to a first solid phase to immobilize the complex onto the first solid phase; collecting the first solid phase having the complex immobilized on the first solid phase; releasing the complex from the collected first solid phase, and then bonding the capture substance in the released complex to a second solid phase to immobilize the complex onto the second solid phase; and acquiring information on the polypeptide from the complex immobilized on the second solid phase, wherein the capture substance that binds to at least one of the first solid phase and the second solid phase binds to a C-terminal region of the polypeptide and is a H31L21 antibody, wherein the capture substance comprises a first capture substance having a first bonding substance and a second capture substance having a second bonding substance, and at least one of the first capture substance and the second capture substance binds to a C-terminal region of the polypeptide; the first solid phase has a first bonding partner that bonds specifically to the first bonding substance and the second solid phase has a second bonding partner that bonds specifically to the second bonding substance; in the step of immobilizing the complex onto the first solid phase, the complex is immobilized onto the first solid phase through a specific bonding between the first bonding substance and the first bonding partner; and in the step of immobilizing the complex onto the second solid phase, the complex is immobilized onto the second solid phase through a specific bonding between the second bonding substance and the second bonding partner, the first solid phase has a first bonding partner that bonds specifically to the first bonding substance and the second solid phase has a second bonding partner that bonds specifically to the second bonding substance; in the step of immobilizing the complex onto the first solid phase, the complex is immobilized onto the first solid phase through a specific bonding between the first bonding substance and the first bonding partner; and in the step of immobilizing the complex onto the second solid phase, the complex is immobilized onto the second solid phase through a specific bonding between the second bonding substance and the second bonding partner, wherein the polypeptide is further brought into contact with a substance for detection which has a labeling substance and binds to the polypeptide to form a complex comprising the polypeptide, the capture substance and the substance for detection, wherein the substance for detection binds to a N-terminal region of the polypeptide, and wherein the polypeptide is amyloid β.