Printer and method for detecting printing paper

A printer comprising:

• a transfer unit configured to transfer printing paper in a printing direction;
• a printing unit configured to print information on transferred printing paper;
• a detection unit installed to face discharged printing paper on a printing paper discharge portion side, and configured to acquire measured values by detecting light while printing paper is transferred or when transfer of printing paper is stopped;
• and
• a control unit configured to collect measured values of the detection unit while printing paper is transferred, to calculate a reference value by using the collected measured values, and to determine whether printing paper has been removed by comparing the calculated reference value with a measured value acquired by the detection unit when transfer of printing paper is stopped;
• and
• wherein the control unit determines whether printing paper has been removed by comparing the calculated reference value with a measured value acquired by the detection unit in real time, transmits a print start command to the transfer unit and the printing unit when it is determined that printing paper has been removed, and maintains the transfer unit and the printing unit in a print waiting state when it is determined that printing paper has not been removed.