1. An electronic system with handle locking device, the electronic system mounted to a shelf in a removable way and comprising:a case, having a first side wall and a second side wall adjoining to each other; and
a handle locking device, disposed at a location where the first side wall and the second side wall adjoin, the handle locking device comprising:
a swinging bracket, a first end of the swinging bracket fixed to the case and a second end of the swinging bracket comprising a hook;
an activation bracket, disposed at the case and movable along a first direction with respect to the case to push the swinging bracket to swing with respect to the case along the first end as a first axle, the hook selectively configurable to be at a locking position or at an unlocking position moving along a second direction different from the first direction with respect to the case when the swinging bracket swings with respect to the case; and
a handle, pivoted to the activation bracket via a second axle and rotatable along the second axle with respect to the activation bracket from a first position to a second position;
wherein when the handle is positioned at the first position, the hook is configured to be at the locking position with respect to the case; when the handle rotates from the first position to the second position, the handle pushes the case to move the activation bracket along the first direction with respect to the case, the activation bracket pushing the swinging bracket accordingly, in which the hook is configured to be at the unlocking position with respect to the case.