Target substance recognition element, detection method and apparatus

A detection device comprising a substrate comprising a plurality of objects of which properties are changed due to the contact with a target substance, means for bringing the target substance into contact with the objects, and means for detecting a change in properties of the objects caused when the target substance is brought into contact with the objects, based on light output when the objects are irradiated with light, wherein the plurality of the objects are located in the direction in which the light for irradiation travels, and the detecting means is means for detecting the change in the properties based on the summation of light output from the plurality of the objects upon irradiation with light.