Provided is a locking mechanism for a flat display device. The locking unit for a single axis rotation flat display device in which an upper body and a lower body are coupled to each other by a rear main hinge, includes: a latch member movable on a guide disposed in the upper body, a locking hole formed in the latch member and a bent portion slantingly bent at a lower end of the latch member which is made of a ferromagnetic material. In a retracted state, the latch member is substantially disposed within the upper body, while in deployed state the latch member protrudes therefrom. A restoration member provides a restoration force to the latch member so as to urge it into its retracted state. A hook member hingedly coupled to the lower body. The hook member having a hook portion whose upper end engages the locking hole. a magnet is installed to or in proximity to the hook member under the hook portion. A push button protrudes from a side portion of the lower body and pushes the hook member so that the hook portion disengages the locking hole when the pushbutton is pressed.