A light source unit of the disclosure includes a plurality of light source sections, a light quantity detector, and a controller. The plurality of light source sections emit rays of colors different from each other. The light quantity detector receives a plurality of color rays emitted by the plurality of light source sections as spatially common light. The controller controls a light emission timing of each of the plurality of light source sections and a gain of the light quantity detector, and measures light quantities of the respective plurality of color rays at different timings and with different gains on a basis of a detection result of the light.