A camera module testing method is applied to a camera module including a camera lens and a photosensitive element. In a step (A), an original image is captured through the camera lens and the photosensitive element. In a step (B), the original image is converted into a gray scale image. In a step (C), the gray scale image is converted into a binary image according to a critical gray scale value. In a step (D), a boundary contour is obtained according to plural pixels of the binary image higher than or equal to the critical gray scale value. In a step (E), a contour center of the boundary contour is obtained. Then, a step (F) is performed to judge whether an optical axis of the camera lens is aligned with an imaging center of the photosensitive element according to the imaging center and the contour center.