The present invention provides a color separation optical system which separates an entrance ray into at least three rays of a first color light, a second color light, and a third color light being different color lights and which guides the three rays respectively to solid-state image pickup elements disposed on different optical paths, the system including a first prism, a second prism, a third prism, and an absorption filter disposed between a second exit surface of the second prism and a third entrance surface of the third prism and configured to absorb the second color light. The third entrance surface of the third prism or a surface of the absorption filter facing the third entrance surface is provided with a second dichroic film which reflects the second color light and transmits the third color light.