Abstract: A printer includes a ribbon supply end including a shaft, a ribbon retrieving end, and a ribbon. The two ends of the ribbon are installed on the ribbon supply end and the ribbon retrieving end respectively. The printer further includes a print head, a driving module for driving the ribbon supply end and the ribbon retrieving end so as to move the ribbon from the ribbon supply end to the ribbon retrieving end, a sensing module installed at one side of the ribbon supply end including a first contact sensor, and a second contact sensor installed between the first contact sensor and the ribbon supply end, and a control module for controlling the printer according to whether or not the second contact sensor can contact the shaft of the ribbon supply end when the first contact sensor contacts the ribbon on the ribbon supply end.