A tamper detection mechanism for detecting tampering when a sub system is removed from a host device may include a screw member that may include a head portion, a major diameter shaft portion and a minor diameter shaft portion. The tamper detection mechanism may also include a through hole provided in the sub system, a lever member, and a detection switch. The lever member may withdraw from said through hole as it is pushed by the major diameter shaft portion when the screw member is tightly screwed, and may advance into the through hole when the screw member is loosened. The detection switch may detect whether the screw member is tightly screwed or loosened based on withdrawal or advancement of the lever member.