A slave device, which is connected to the file system of a host device and shares a storage device with the host device, and a data sharing method between the host device and the slave device are provided. The slave device has a storage device and is connected to the host device through a predetermined coupling device. The slave device includes a media driver for performing connection to a file system of the host device according to a predetermined protocol such that at least part of the storage device operates as a storage device of the host device. Accordingly, the storage device within the slave device operates as the storage device of the host device in a universal application program of the host device, thereby allowing the host and slave devices to share at least part of the storage device of the slave device using a universal application.