A detection device includes a flow channel for a fluid sample, a suction section adapted to draw the fluid sample into the flow channel, an optical device disposed in the flow channel, a light source adapted to irradiate the optical device with light, a light detection section adapted to detect light emitted from the optical device, a microbalance sensor chip having a piezoelectric substrate provided with an oscillation electrode, and disposed in the flow channel, and a quantitative analysis section adapted to perform quantitative analysis on the fluid sample based on output from the light detection section and the microbalance sensor chip. The optical device has a metal nanostructure including projections ranging in size from 1 through 1000 nm, and emits light representing the fluid sample adsorbed to the metal nanostructure.