To prevent a user from getting an electric shock even if his/her hand touches a connector of power supply for lamp in a case body when a lamp box of a liquid crystal projector is taken out.

If a lamp box 2 in a casing 1 of a liquid crystal projector causes a failure, its lid 3 is opened to take the lamp box 2 out of it. Infrared rays from a light emitting part 11 enter a light receiving part 12 by opening (removing) the lid 3. A signal from the light receiving part 12 is amplified in an amplification part 13, is input into a judging part 15 through a control part 14, judges that the lid is opened, and drives a lamp SW 17 to OFF by a drive part 16 to shut off power supply supplied from lamp power supply to the lamp box 2 through a connector 4.