1. An imaging device comprising: an image capturing part which captures an image continuously; a first detection part which detects one or more subjects in an image captured by the image capturing part; a second detection part which follows and detects the one or more subjects detected; and a control part which includes a setting part setting a part of the image as a limited region, and causes, after the first detection part detects the one or more subjects in the captured image, the second detection part to follow and detect a subject in an image captured subsequently to the captured image, and causes the first detection part to detect a subject in the limited region.