Focus detection device, focus detection method and imaging apparatus

A focus detection device comprising:

• an imaging element that is provided on a light path of a light flux incident via an optical system and that has a plurality of pixels of charge storage type two-dimensionally arranged;
• a storage controller configured to control the imaging element to sequentially store charges in pixels arranged in a first direction among the plurality of pixels to generate a first output and configured to control to sequentially store charges in pixels arranged in a second direction opposite to the first direction to generate a second output;
• and
• a focus detector configured to detect a focus adjustment state of the optical system based on a combination of both the first output obtained when the storage controller sequentially performs storage control in the first direction and the second output obtained when the storage controller sequentially performs storage control in the second direction.