An interlocking device for locking a case includes first and second interlocking members. The first interlocking member is formed with a notch. The second interlocking member is formed with a button that is operable to rotate the second interlocking member from a first position, in which the first and second interlocking members engage each other and in which the button is received in the notch, to a second position, in which the first and second interlocking members disengage from each other and in which the button moves out of the notch.