A printing system includes: a conveyance controller configured to control a conveyor, the conveyor being configured to convey paper having a printing surface in which label portions are formed at predetermined intervals; a sensor configured to irradiate light on the paper conveyed by the conveyor to detect reflected light of the irradiated light; a detector configured to detect an output of the sensor; a moving average calculator configured to calculate moving averages of voltage values based on the output of the sensor detected by the detector; and a determiner configured to determine that a portion between an adjacent pair of the label portions has been detected based on the moving averages of the voltage values calculated by the moving average calculator, and the output of the sensor.