In order to improve the detection accuracy of a reflection spectrum, a detection device for intermolecular interaction is provided with a detector (10) which has a ligand (16), a white light source (20) which emits white light, a spectroscope (30) which detects the spectral intensity of received light, a light transmission unit (40) which has a first light transmission path (41) for transmitting the white light from the white light source to the detector, a second light transmission path (42) for transmitting reflected light of the white light from the detector to the spectroscope, and a third light transmission path (43) for transmitting the white light from the white light source to the spectroscope, a switching unit (80) which performs switching between a reflected light receiving state in which the transmission of the reflected light of the white light in the detector to the spectroscope via the first and second light transmission paths is enabled and a white light receiving state in which the transmission of the white light from the white light source to the detector via the third light transmission path is enabled, and a control unit (50) which controls the switching unit and the spectroscope to perform control for detecting the spectral intensities in the white light receiving state and the reflected light receiving state, respectively.