To obtain a diagnostic apparatus by which the existence of an object to be detected can be judged simply by a method wherein a sample which exists in a liquid is reacted with a labeled antibody or the like and a filter which is used to sort a reacted substance from an unreacted substance according to a physical size is used.

In a diagnostic kit, a sample which exists in a liquid is reacted with an antibody which is bonded immunologically to the sample or with an antibody which is bonded immunologically to the sample and which is labeled. After that, a filter 2 which sorts a reacted substance from an unreacted substance according to a physical size is used, and the existence of the sample is detected or the sample is measured quantitatively. Then, when one kind of a polyclonal antibody or two or more kinds of monoclonal antibodies exist, an object to be detected can be detected, and a complicated selection means to combine antibodies is not required. In addition, the diagnostic kit is important in order to detect a human villous gonad stimulant hormone which is utilized especially as a marker for the diagnosis of a pregnant woman.