An imaging apparatus includes an imaging device, and an optical system configured to image light from an imaging subject on the imaging device. The optical system includes a group of lenses and an aperture diaphragm. When NP point is defined as a point where an extended linear component in an object space of a principal ray located in a Gauss region and selected from among principal rays passing through a center of the aperture diaphragm of the optical system crosses an optical axis of the optical system, D represents a diameter of a lens at the closest side to the imaging subject, and LN represents a distance from a lens surface of the lens at the closest side to the imaging subject to the NP point, a formula; 0≦LN≦D (1) is satisfied.