1. An imaging apparatus comprising: a planar image acquisition unit configured to acquire a planar image of a subject; a tomographic image acquisition unit configured to acquire a tomographic image of the subject; and a polarization adjustment member disposed in a common optical path of a portion of an optical system in the planar image acquisition unit and a portion of an optical system in the tomographic image acquisition unit and configured to adjust polarization states of a measuring beam for the planar image and a measuring beam for the tomographic image.