PURPOSE: To improve the operability of a keyboard by lowering the height of a key top at the time of carrying to thin the whole device, heightening the height of the key top at the time of use to secure the necessary key stroke, concerning a book type information processor.

CONSTITUTION: By using an air spring to seal the compressed air composed of a key piston 2 and a key cylinder 4 in the elasticity recovery system of a key, the key operation is performed, all key cylinders 4 are connected to an inter-keyboard pipe 6 to make one closed space, an opening and closing valve 9 is provided, the compressed air can be enclosed and discharged and made variable, and when the discharging is performed, respective keys are lowered to the lowest position, and when the compressed air is enclosed again, a pump 8 is used.