An imaging device includes an image sensor provided at an imaging position of a photographing optical system, at least one optical element provided in front of the image sensor, a hermetically-sealing holding member which hermetically seals and integrally holds the image sensor and the optical element, a support member which supports the hermetically-sealing holding member and is prevented from tilting relative to an optical axis of the photographing optical system, and an angle-adjusting device which allows the hermetically-sealing holding member to tilt relative to the support member so as to change the tilt angle of the image sensor and the optical element with respect to the optical axis of the photographing optical system upon assembly.