An image monitoring apparatus includes a casing, a camera module in the casing, and a lighting module disposed on the casing and located above or under the camera module on a plane corresponding to a vertical angle of view of the camera module. A horizontal light-emitting plane of a LED of the lighting module is perpendicular to the plane corresponding to the vertical angle of view. A lens of the lighting module covers the LED and has a convex light-exit surface, a bottom surface, and a concave light-entrance surface. A long axis of the convex light-exit surface is located at the horizontal light-emitting plane. A section thickness of the lens from the concave light-entrance surface to the convex light-exit surface along the long axis is greater than a section thickness of the lens from the concave light-entrance surface to the convex light-exit surface along a normal of the bottom surface.