An image taking apparatus which can perform a focusing operation quickly is described. The image taking apparatus comprises a light splitting unit which splits a light flux from the image-taking lens into a plurality of light fluxes, a view finder optical system for observing an object image formed by the light flux from the image-taking lens, an image pickup element which photoelectrically converts the object image to an electric signal and a focus detection unit for detecting the focusing state of the image-taking lens according to a phase difference detection system. Here, the light splitting unit changes between a first state in which the light flux is directed to the view finder optical system and the focus detection unit and a second state in which the light flux is directed to the image pickup element and the focus detection unit.