An optical apparatus which can be focused on an object included at an arbitrary position in an image-taking area with simple operations, is disclosed. The optical apparatus according to the present invention comprises a focusing state calculating circuit which derives information indicating a focusing state of an optical system based on an output signal from an image-pickup area which corresponds to part of an image-pickup device, and a storage circuit which stores the position of the image-pickup area in the image-pickup device. The optical apparatus also comprises a setting system which moves the image-pickup area, stores the position of the image-pickup area in the storage circuit, and sets an image-pickup area which has been stored in the storage circuit as the image-pickup area in performing focus adjustment control.