The present invention relates to a novel method for detecting a detection object in a sample, and a detection device using the same. The detecting method of the present invention uses a “bridge composite” in which gold nanoparticles and an antibody specific to a detection object are coupled in order to induce a sufficient coupling reaction between the antibody and the detection object, thereby improving reactivity. Accordingly, since excellent resolution is provided, the method of the present invention has advantages of enabling accurate concentration measurement of a detection object in a sample, and amplifying a measurement signal. In addition, the method of the present invention can effectively detect small molecules such as hormones, vitamins, etc. having a small molecular weight.