Abstract: A tiltable and rotatable base assembly for a monitor includes a substantially rectangular base plate, a rotatable plate having a semi-spherical shaped well for tiltably receiving a semi-spherical shaped bottom wall of an upwardly opening box-like housing, the semi-spherical shaped two portions having approximately the same curved rate. When the monitor is rotated for adjusting the degree of rotation, the box-like housing and the rotatable plate are rotated simultaneously with respect to a support plate on which the rotatable plate and the box-like housing are mounted one above the other. When it is desired to tilt the monitor, the box-like housing is tilted in the semi-spherical well. A detent protrusion is provided for successively detentable engaging with the bottom of the rotatable plate.