Detecting and processing multi feeding

An image forming apparatus comprising:

• an image forming portion;
• a print medium transporting device to pick up a print medium loaded in a loading portion and transport a picked-up print medium;
• a print medium alignment portion to align a leading end of the transported print medium and supply the aligned print medium to the image forming portion;
• a first sensor to sense the print medium that passes through a feed roller of the print medium transporting device;
• a processor;
• and
• a non-transitory computer readable medium storing computer-executable instructions that when executed by the processor cause the processor to:
• based on a measured value with respect to the print medium sensed by the first sensor and a multi-feeding determination reference value corresponding to a sheet of the print medium, detect multi-feeding of the print medium and process the detected multi-feeding by controlling the print medium transporting device and the print medium alignment portion to, based on a predetermined gap distance, control transport of picked-up print medium by controlling a distance of a gap between a first sheet of picked-up print medium and a second sheet of picked-up print medium,
• wherein the controlled distance between the first sheet of print medium and the second sheet of print medium corresponds to a distance between the first sensor and a second sensor.