1. An imaging apparatus comprising: an image sensor configured to capture an object image; an evaluation value calculation unit configured to calculate a focus evaluation value indicating a contrast of an object image included in a focus detection area, using an image signal output from the image sensor; a first focus detection unit configured to move a focus lens by a unit driving amount smaller than a predetermined threshold to detect a focus state based on a change in the focus evaluation value; a second focus detection unit configured to move the focus lens by a unit driving amount equal to or larger than the predetermined threshold to detect the focus state based on a change in the focus evaluation value; and an object detection unit configured to detect the object using the image signal, wherein, if the focus evaluation value is smaller than a predetermined evaluation value and the object has been detected, the focus state is detected using the first focus detection unit without using the second focus detection unit.