An apparatus having a line of sight detection device, comprises a viewfinder for observing a target object, a line of sight detection means for detecting a position of line of sight in the viewfinder of a user, focus detection means being possible to select a first operation mode for performing a first focus detecting operation or a second operation mode for performing a second focus detecting operation, and being possible to perform a focus detection to each of a plurality of focus detecting areas arranged in the viewfinder, range setting means for setting a plurality of determination range including the focus detecting areas, and for changing a size of the determination range to be set in accordance with the selection of the operation mode of the focus detecting means, selecting means for determining which determination range includes the position of line of sight detected by the line of sight detecting means, and for selecting at least one focus detecting area among the plurality of focus detecting areas, and focus adjusting means for adjusting a focus of an optical system based on a focus detecting result of the selected focus detecting area.