1. A focus detection apparatus comprising: an image pickup unit configured to perform photoelectric conversion on a subject image to generate an image signal; a generation unit configured to generate a focusing signal from the image signal corresponding to a focus detection area; a first detection unit configured to detect a first subject region from the image signal; a second detection unit configured to detect a second subject region, in which the first subject region can be estimate, from the image signal; a setting unit configured to set the focus detection area according to a primary subject; and a control unit configured to perform focus detection based on the focusing signal, wherein the setting unit, in a case where the primary subject corresponds to the first subject region detected by the first detection unit, sets the focus detection area to the first region, and, in a case where the primary subject corresponds to the first subject region estimated based on the second subject region detected by the second detection unit, sets the focus detection area to a second region that is larger than the first region.