A mobile terminal apparatus includes upper and lower cases; a sliding-rotation-mechanism performing an opening-direction-sliding-movement through a sliding-supporting plate at opening manipulation, allowing the upper case to stand up at a predetermined angle with respect to the lower case after the opening-direction-sliding-movement, performing closing-direction-rotation-movement, standing up at the predetermined angle through the sliding-supporting plate at closing manipulation, and performing closing-direction-sliding-movement through the sliding-supporting plate after the closing-direction-rotation-movement; and a flexible board disposed so that electrical parts of the upper and lower cases are electrically connected to each other and a portion corresponding to a predetermined length just after the portion exposed from the upper case is adhered to the sliding-supporting plate through an adhesive.