A tray used to place granular materials on a reading surface of an image reading device has provided thereto a transparent bottom plate, a background vertically upstanding relative to the bottom plate, and reflective elements arranged at predetermined intervals parallel to the background. In order to enable an imaging means of the image reading device to receive a side view image of the granular materials in the thickness direction thereof with the granular materials placed on the bottom plate of the tray, the tray is provided with a technical means for bending and guiding, by the reflective elements, light from the granular materials in the thickness direction thereof to the direction of the optical axis of the imaging means.