An testing device for lens module includes an image sensor, a light source assembly, a testing tray, a detecting device, and a processor. The light source assembly is aligned with the image sensor. The testing tray is disposed between the light source assembly and the image sensor, and defines a plurality of through holes for receiving lens modules. The detecting device is configured for detecting whether the lens module to be tested is tilted. The processor controls the moving of the image sensor and the testing tray. The processor is capable of stopping the moving of the image sensor and the testing tray when the detecting device detected the lens module to be tested is tilted.