A detection device includes an optical device, a suction section adapted to suck the fluid sample in the optical device, a light source adapted to irradiate the optical device with light, a light detection section adapted to detect light emitted from the optical device, and a control section adapted to perform drive control on the suction section. The optical device emits light reflecting the fluid sample to be adsorbed. The control section sets a suction flow velocity of the fluid sample on the optical device to V1 in a first mode including a period of performing detection by the light detection section, sets the suction flow velocity of the fluid sample on the optical device to V2 (V2>V1) in a second mode, and switches between the first mode and the second mode based on a signal from the light detection section.