A tilt sensor including a body, an LED, a first photosensitive device, a second photosensitive device, and a moving thin-element is provided. The body has a movement region, a first containing region, a second containing region, and a third containing region. The first, second, and third containing regions have an opening respectively and are connected with the movement region through the openings. The LED providing a light beam is disposed in the first containing region. The first and second photosensitive devices are disposed in the second and third containing regions respectively. When the body tilts toward different tilt directions, the moving thin-element moves in the tilt direction, allowing the light beam provided from the LED to reflect directly to the first and second photosensitive devices, or shielding the light beam provided from the LED from being transmitted to the first and second photosensitive devices.