A flash memory device (8) includes a memory module (2), a screw (3), a gear (4) and a case (1). The memory module (2) has a plug (22) formed at one end thereof. The screw (3) has a first end (30) and a second end (31) opposite to the first end (30). The first end (30) is mounted on the memory module (2). The gear (4) is positioned on the screw (3) and is rotatable relative to the screw (3). The case (1) includes a receiving cavity for receiving the memory module (2), and a first inner case (10) with a first rack (1002) engaging with one side of the gear (4). The first rack (1002) extends along a length direction of the case (1). The memory module (2) has a second rack (2011) engaging with another side of the gear (4). The second rack (2011) extends along the length direction too. The screw (3) is located between the first rack (1002) and the second rack (2011).