According to an aspect, a detection device includes a plurality of light-receiving elements configured to receive light, and a light guide portion one surface of which faces the light-receiving elements. The light guide portion includes a plurality of light guide paths provided throughout from the one surface to the other surface of the light guide portion, and a light-absorbing portion having higher absorbance of the light than that of the light guide paths. When viewed from a direction in which the light-receiving elements and the light guide portion are stacked, more than one of the light guide paths overlap one of the light-receiving elements.