Immunoassay device and immunoassay method using the same

An immunoassay device, comprising:

• a membrane portion;
• a labeled substance dotting portion provided on the membrane portion, wherein the labeled substance dotting portion comprises a pad of an absorbable material which contains a labeled substance and wherein the labeled substance is in mobilizable/diffusively bound form in the pad;
• a specimen dotting portion provided on the labeled substance dotting portion;
• a developing solution-supplying portion having a breakable solution reservoir, wherein the breakable solution reservoir contains a developing solution;
• a water-absorbable pad, wherein the developing solution-supplying portion and the water-absorbable pad are at opposite ends of the membrane portion;
• and
• a detection portion provided between the labeled substance dotting portion and the water absorbable pad, wherein an antibody or antigen is immobilized in the detection portion;
• wherein the labeled substance dotting portion is provided between the detection portion and the developing solution-supplying portion and yet at a position where a ratio LX/LT is less than 0.5, wherein LX is the distance from the longitudinal center of said labeled substance dotting portion to an end of said water-absorbable pad, the end of which is present at an upstream side of the solution transferring direction of the developing solution, and LT is the distance from said end of said water-absorbable pad to an end of said developing solution-supplying portion, the end of which is present at a downstream side of the solution transferring direction of the developing solution.