Abstract: A securing device includes a central rod extending from the driving press to be movably mounted on a top board of the computer main frame and a base having an engaging plate movably attached to the base via a first spring which is sandwiched between the base and the engaging plate and a lateral rod securely extending away from the engaging plate to selectively engage with a free end of the central rod. When the central rod is longitudinally moved, the longitudinal movement of the central rod drives the lateral rod to move laterally and thus a hook which is formed on a side face of the engaging plate for extending through the first side board and the second side board to secure engagement between the first side board and the second side board is away from the first side board and the second side board and the second side board is free from engagement with the first side board.