In order to enable mounting of a cabinet 1 having a display unit to a supporting base 9, axial members 121 and 131 in the shape of a regular polygonal prism are disposed in the cabinet 1 and fitting holes 91 and 92 into which the regular polygonal prisms can be fitted, respectively, are disposed in the supporting base 9. By opening and then closing, or opening and then moving the axial members 121 and 131, the user can fit or remove them into or from the fitting holes 91 and 92, respectively, so as to mount or demount the cabinet to or from the supporting base. By tilting the cabinet by an angle when fitting the axial members into the fitting holes, respectively, the user can change the rotational attitude of the cabinet 1 with respect to the supporting base. Thereby, the user can use the display unit at different times and at different positions with simple manipulations.