Abstract: A light source includes: light-emitting elements of different colors, forming a light-emitting element group; a light-emitting element base on which the light-emitting elements are placed in a way that a main optical axis direction intersects a placement surface of the light-emitting element base; a reflection unit including a reflection surface configured to narrow light emitted from the light-emitting element group, a front-side opening portion formed on a front side of the reflection unit in the main optical axis direction, and a rear-side opening portion formed in a rear side of the reflection unit in the main optical axis direction; and a diffusing portion placed in front of the reflection unit in the main optical axis direction, and configured to diffuse the light. In the reflection unit, an area of the front-side opening portion is smaller than that of the rear-side opening portion.