To provide a carburizing treatment method by which uniform carbon concentration at the surface of a material to be treated can be attained, and to provide a carburizing treatment system using the method.

In performing carburizing treatment while varying the pressure in a heating chamber 2 by heating a work in the heating chamber 2 up to carburizing temperature in nitrogen atmosphere and then alternately repeating the evacuation inside the heating chamber 2 and the supply of gaseous chain hydrocarbon, a charging tank 21 having prescribed capacity is used and the gaseous chain hydrocarbon having a prescribed pressure sufficiently higher than the pressure in the heating chamber 2 is temporarily introduced into the charging tank 21 and then discharged into the heating chamber 2.