Immunochromatography

A method of immunochromatography comprising:

• a concentration step of concentrating a solution capable of containing an antigen by ultrafiltration to obtain an antigen-concentrated solution, wherein the solution capable of containing an antigen is urine;
• a spreading step of, by adding dropwise the antigen-concentrated solution directly onto a gold colloid holding pad, which is a pad that holds modified gold particles which are gold particles modified with a first binding substance capable of binding to an antigen in the antigen-concentrated solution, of an insoluble carrier having the gold colloid holding pad and a reaction site at which a second binding substance capable of binding to the antigen has been immobilized, spreading gold particle composite bodies on the insoluble carrier, in a state where the gold particle composite bodies which are composite bodies of the antigen and the modified gold particles are formed;
• a capturing step of capturing the gold particle composite bodies at the reaction site of the insoluble carrier;
• and
• a silver-amplifying step of silver-amplifying the captured gold particle composite bodies,
• wherein a molecular weight cut-off of an ultrafiltration membrane that is used in the ultrafiltration is 1 kDa to 5 kDa.