The detection system according to the present invention has a detection chip, a light source, and a detection unit. The detection chip has a housing that has an opening at an upper portion, and a reaction field for trapping a substance to be detected, the reaction field being arranged on an inner surface of the side walls included in the housing. The light source irradiates the detection chip with light from the outside such that evanescent light or surface plasmon resonance is generated under the reaction field. The detection unit detects light which is emitted from the detection chip when the light source irradiates the detection chip with light, and the amount of which changes depending on the amount of the substance to be detected trapped in the reaction field.