To provide a keyboard device enabling smooth alter operation by one hand even if it is the same keyboard layout as the keyboard for both hands in a keyboard for inputting a character, a figure, etc. into an electronic device such as a personal computer and a multifunctional cellular phone.

The keyboard is expanded three dimensionally in a space surface in a range where one (the thumb or another finger) or a plurality of fingers of one hand move freely in a condition where a wrist is fixed, and keys are arranged according to an array according to a keyboard for both hands. Thereby, a keyboard surface has the shape expanded in an inner surface of a solid with a cross section which is U-shaped, V-shaped, pentagonal, etc. According to an intended use, it has functions for folding, angle adjustment, etc.