The present invention relates to a densitometry device that can perform suitable densitometry with minimum required light amounts and can achieve space savings. An angle .theta. between a reference optical axis of a light source, which is an LED chip, and an optical axis, according to a photoelectric conversion element, of a density measurement optical system is set to, for example, 52.degree.. Light-emitting chips, which emit each of red, green and blue light, are provided inside a cannon shell-shaped light-emitting portion. These light-emitting chips are arranged in a straight line along a direction of conveyance of a color patch chart. Consequently, inclination angles of the light-emitting chips with respect to a measurement axis of the density measurement optical system will always change consistently with each other, and no difference between the inclination angles of the different colors will occur.