An optical apparatus is disclosed, with which focus detection areas of different size and/or position can be stored. The optical apparatus includes a first operating member which is operated changing at least one of a size and a position of a focus detection area, a memory storing a plurality of focus detection areas which differ from each other in at least one of size and position, a second operating member which is operated for setting one of the plurality of stored focus detection areas as a to-be-used focus detection area for detection of the focus state of an image-taking optical system. The apparatus further includes a controller performing storage and setting processes of the focus detection areas and a focusing control of the image-taking optical system.