An unpowered stop mechanism includes a mounting seat, a driving member, and a stop assembly. The stop assembly is located on the mounting seat and oppositely positioned to the driving member. The stop assembly includes a guide member, a stop member, and a hinge arm. The stop member is received within a guide slot defined in the guide member. The hinge arm is pivotably coupled to the guide member. The hinge arm protrudes from the guide member and is oppositely positioned to the driving member. The driving member drives the hinge arm to drive the stop member to retract within the guide slot. Then the driving member is moved to be spaced from the hinge arm, the stop member is driven by a resilient member received within the guide slot to protrude out of the guide slot.