A low temperature carburizing method according to the present invention comprises: step (a) for pre-processing a metal to be processed; step (b) for inputting the metal to be processed to a reaction chamber and heating the same to a set temperature; step (c) for forming a vacuum atmosphere in the reaction chamber and introducing a reaction gas thereinto at a predetermined pressure to accelerate carburization; step (d) for supplying the reaction gas to the reaction chamber at a pressure equal to or lower than the pressure of the reaction gas of step (c) to spread carburization; and step (e) for repeating step (c) and step (d) at predetermined time intervals.