An innovated design of keyboard for keying in commands to a PDA, particularly a collapsible type that can be folded for storage and convenient carrying purposes, and its two sides can be unfolded and compressed to a fixed status to minimize measurements, which comprising a left keyboard and a right keyboard, and a connecting board to enable connection of the left keyboard with a mobile track plate, forming a foldable and movable joint. Furthermore, provided on one side of the mobile bottom plate of the right keyboard and between two recesses is a formation of a protruded insert, thereby when the right keyboard and the left keyboard are pushed and inserted in position, the protruded insert on the mobile bottom plate of the right keyboard is inserted into the insert groove on the bottom plate of the left keyboard.