One embodiment of the invention provides a lens-testing apparatus being used for testing a lens device. The lens-testing apparatus comprises a light module, at least one first and second image sensors, and at least one image sensor module. The light module generates a patterned light beam passing the lens device. The first and second image sensors receive first and second portions of the patterned light beam; the first image sensor is disposed between the second image sensor and the lens device. The image sensor module receives a substantially parallel third portion of the patterned light beam, and comprises a third image sensor and a collimator. The third portion of the patterned light beam is focused onto the third image sensor by the collimator; the distance between the first image sensor and the lens device is smaller than the distance between the second image sensor and the lens device.