A portable information terminal apparatus includes a portable information terminal unit having a display surface capable of displaying the information and a cradle on which the portable information terminal unit can be detachably mounted. When the portable information terminal unit is loaded on the cradle, data can be transmitted/received to or from another electronic equipment through the cradle. The portable information terminal apparatus includes a lock mechanism for switching the portable information terminal unit between a locked state and an unlocked state when the portable information terminal unit is loaded on the cradle. The portable information terminal unit includes an information readout unit for reading out the contact information and a controlling unit for controlling the lock mechanism when the information readout unit has read out the preset contact information.