An image taking apparatus performs a focusing operation quickly and includes a light splitting unit which splits a light flux from an image-taking lens into a plurality of light fluxes, a view finder optical system observing an object image formed by the light flux from the lens, an image pickup element which photoelectrically converts the object image to an electrical signal and a focus detector detecting the focusing state of the lens according to a phase difference detector. Here, the light splitting unit changes between a first state for directing the light flux to the view finder optical system and the focus detector, a second state for directing the light flux to the image pickup element and the focus detector, and a third state in which the light flux is directed only to the image pickup element.