A tilt sensor includes a body, a light emitting device, a first photosensitive device, a second photosensitive device, and a moving element. The body can tilt in a plurality of tilt directions. The light emitting device is disposed at the body for providing a light beam. The first photosensitive device is disposed at the body and at one side of the light emitting device. The second photosensitive device is disposed at the body and at another side of the light emitting device. The moving element is disposed at the body. When the body tilts toward different tilt directions, the moving element moves toward different tilt directions so that the light beam emitted by the light emitting device directly transmits to the first photosensitive device and the second photosensitive device or is sheltered from directly transmitting to at least one of the first photosensitive device and the second photosensitive device.