Case for electronic device, electronic device using the same, and notification method thereof

Disclosed are a case for an electronic device, an electronic device including the case, and a notification method thereof. The case for the electronic device having a lateral side, a back side, and a display configured to emit light may include: a body that is fastened to the electronic device; and a light guide unit that is formed in the body, and guides the light emitted from the display of the electronic device to at least one of the lateral side or the back side of the electronic device to be output to the outside.