The present disclosure relates to a garment folding machine and a method of controlling the garment folding machine, in which it is possible to effectively prevent damage to a garment by controlling and reducing tension after detecting and determining a situation in which the tension is applied to the garment during a process of conveying or folding the garment, and it is possible to allow the folding machine to smoothly perform vertical folding by disposing the garment at an appropriate position in order to perform the vertical folding.