an adjustable hinge device is provided for a foldable apparatus in accordance with the present invention . the foldable apparatus , such as a portable mobile phone , comprises a cover and a body connected by the hinge so as to make the cover rotatable relative to the body between a fully opened position and a fully closed position . when the cover rotates to the fully opened position , a maximum opening angle is defined . according to the relative movement between a rotatable portion and a fixed portion of the adjustable hinge , the maximum opening angle can be adjusted to fit different requirements .