A microwave oven, is designed such that its switches accurately sense whether a door is open or not when opening or closing the door, thus preventing microwaves from leaking out. The microwave oven includes a hook unit, a hook locking unit, a locking step, and a sensing switch. The hook unit is mounted to the door functioning to open or close a cabinet. The hook locking unit is installed in the cabinet to engage with the hook unit. The locking step is provided in the hook locking unit to catch the hook unit when the hook unit enters the hook locking unit. The sensing switch is installed in the hook locking unit to sense whether the hook unit enters the hook locking unit. A screw holding unit is provided on a predetermined portion of the locking step to hold a setscrew which functions to mount the hook locking unit to the cabinet.