IMAGE PICKUP APPARATUS AND CAPSULE ENDOSCOPE

PROBLEM TO BE SOLVED: To provide an imaging device and capsule endoscope that include an image formation optical system in which the image formation optical system is advantageous to a correction of a chromatic aberration without making a Petzval sum of an optical system small, is easy to have the number of lens pieces reduced and to be downsized, and can obtain an excellent optical performance.SOLUTION: An imaging device comprises: an image formation optical system that includes a brightness stop S determining an axial light flux, and a diffraction optical plane being arranged at a position different from an arrangement position of the brightness stop S; and an imaging unit that is arranged on an image side of the image formation optical system, and includes a light reception surface of a non-plane curved concavely toward the image formation optical system, and the diffraction optical surface is arranged at a position satisfying a conditional expression (1). 0.1