The present invention relates to a combination product for detecting a target marker simply and with high sensitivity. More specifically, the present invention relates to a combination product for detecting a target marker in a biological sample in combination with a target marker binding molecule which is capable of binding specifically to the target marker in the biological sample, the combination comprising, at least: (a) a first binding agent comprising a first binding molecule which is capable of directly or indirectly binding specifically to the target marker binding molecule, and a labeling substance; (b) a linker molecule which is capable of binding specifically to the first binding agent; and (c) a second binding agent which is capable of binding specifically to the linker molecule, and comprises a second binding molecule and a labeling substance.