An imaging-element inclination adjustment mechanism including at least one adjustment member attached to an imaging-element unit in a manner that a position of the adjustment member is adjustable relative to the imaging-element unit, the imaging-element unit holding an imaging element; at least one support member secured to a housing; and at least one securing member engaged with the adjustment member and attached to the support member. The position of the adjustment member is adjusted relative to the imaging-element unit to adjust a position of the imaging-element unit relative to the support member. The support member supports the imaging-element unit via the adjustment member at each of at least three positions.