The present invention relates to the monitor having ribs for fixing a CRT comprising a CRT, a shield cover which is assembled enclosing said CRT from behind and a monitor case composed of at least two covers which enclose said CRT and said shield cover, and are joined one another by joining members, wherein the ribs for fixing the CRT are formed protruding from the inner surface of said monitor case in accordance with the shape and contours of the outer periphery of the CRT so that the CRT is fitted into the ribs and secured by joining force between said covers which are joined by said joining members. Since the CRT is fixed by the binding force between the covers comprising the monitor case and by said fixing ribs for the CRT, fixing lugs at each edges of the CRT are not necessary. Accordingly, there arises a merit that the size of the monitor can be reduced close to the actual screen size. And various kinds of incidental expenses for transportation and loading of the CRT are also reduced since the size of the CRT can be reduced.