In a focus detecting device of the type in which light fluxes passing through two areas obtained by dividing a pupil of an image forming lens are received by a sensor to detect a phase difference, pixels of the sensor are disposed in such a manner that the sensor has the light-receiving sensitivity in different directions with respect to the luminance distribution, and the phase-difference detection and the contrast detection are performed according to the direction of the light-receiving sensitivity so as to perform appropriate focus detection.