PURPOSE: To eliminate the need for an observation hood and to enable a user to observe outdoors without being affected by the direction of a main body by providing the rear part of an LCD(liquid crystal display device) with an aperture which is arbitrarily openable and closable by a cover and constituting the device in such a manner that the cover is opened outdoors and natural light is taken in from the rear part of the LCD.

CONSTITUTION: The rear part of the LCD is provided with the aperture which is arbitrarily openable and closable by the cover 2. The LCD is usually used in the state of holding the cover 2 closed at the time of using the device indoors. The light of a fluorescent tube 6 for a back light is made to glow indoors from the rear surface of an LCD display module 4 by a filter 5 for guiding and diffusing the light but the cover 2 of the aperture is opened and the display of the LCD is observed by taking the external light from the rear surface of the LCD through the filter 5 at the time of using the device outdoors. The cover 2 of the aperture is made openable and closable by means of, for example, a hinge 10 and is fixed by a stopper 11 at the time of closing the cover. As a result, the observation of waveforms outdoors is made possible without separate prepn. of the hood for observation.