To provide a bioassay system or the like, which can solve the problem of allocating spaces above detecting sections and can also stabilize servo-controlled operation of a disk-shaped plate.Provided is a bioassay system (U) or the like, which is equipped with at least means for immobilizing a nucleotide chain, a peptide, a protein, a lipid, a low molecular-weight compound, a liposome or any other biological substance as a detection substance (D) in a detecting section (3), dropping a target-substance containing solution (S) onto the immobilized detection substance (D), and causing the detection substance (D) and the target substance (T) to interact with each other to prepare a reaction product (R); and means for condensing fluorescence (F), which has been emitted from the fluorescence-labeled substance (D) by irradiating excitation light (P) of a specific wavelength onto the reaction product (R), by a lens (5) arranged on a side of a back surface (102) of the reaction section (3) to determine an intensity of the fluorescence (F).