Disclosed is a folder driving device for a portable device. The device comprises first and second shaft support parts formed at one end of a body element of the portable device, wherein said first and second shaft support parts are spaced apart from each other by a predetermined distance and opened at their respective ends facing to each other; a cylindrical hinge housing connected to a folder of the portable device, wherein said cylindrical hinge housing is positioned between the first and second shaft support parts and opened at both ends thereof; a hinge cam coupled to the second shaft support part in the hinge housing in a manner such that it is prevented from being rotated and allowed to be moved in an axial direction; a hinge shaft placed in the hinge housing and cooperating with the hinge cam to determine folder opening and closing positions; an elastic member placed between the hinge cam and the hinge housing to apply elastic force to the hinge cam for biasing the hinge cam against the hinge shaft; and driving means for transmitting rotation force to the hinge shaft.