To prevent an imaging element from being adversely affected due to warping of an imaged surface.

In this imaging device, an optical filter 10 has defocusing correction characteristics by processing the optical filter 10 to increase thickness of its periphery in accordance with warping of a peripheral part of the imaged surface 22 if the peripheral part is warped backward. If the imaged surface 22 is warped in the reverse direction, thickness of a central part of the optical filter is increased. When amount of warping of the imaged surface 22 is f, difference d in thickness of the optical filter 10 can be calculated by the following expression: d=f/(1-1/n), wherein n denotes refractive index of a first birefringent plate 11.