Abstract: The present invention discloses a notebook computer having a pen input device comprising: a main body having a hard disk drive and a floppy disk drive formed inside its case, a keyboard installed on the case, and the rest of any peripheral equipment; a display having a central processing unit and a memory device and using a liquid crystal display panel as a monitor; a first connector formed at a hinge of the main body to be connected with the display; a second connector formed in the display to be combined correspondingly with the first connector, in order to be used both as a notebook computer and a pen computer by a turnabout rotation and connection of the first and second connectors. Therefore, such a portable computer can be adapted into two kinds of computers and is convenient and easy to carry.