A screen display processing apparatus used for a portable terminal apparatus includes a moving unit configured to relatively move a plurality of cases of the portable terminal apparatus, a detection unit configured to detect a parameter value representing a degree of relative movement of the cases, a determination unit configured to determine based on the parameter value whether a shape of the portable terminal apparatus changes, and a first control unit configured to control a function about the screen display provided in the portable terminal apparatus in accordance with the parameter value and the change or no change in the shape.