An indicating instrument including a light guiding system having at least a first and second light guides, a sensor disposed at a first end of the first light guide and configured to receive incident ambient light that has traveled through the first light guide, a light-emitting device disposed at a first end of the second light guide and configured to emit light through the second light guide, and a covering body disposed at a second end of the first and second light guides that is opposite to the first ends. Further, the incident ambient light is incident upon the covering body and travels through the first light guide and is received by the sensor, and the light emitted by the light-emitting unit travels through the second light guide and exits the covering body.