This invention aims at providing a method of continuously carburizing a metal strip, which is capable of providing industrially optimum carburization conditions while attaining non-soot-generating atmospheric data, desired carburization concentration distribution and desired carburization rate, in a case where a strip passed through a carburization furnace is carburized continuously in a surface reaction rate-governing area in which the carbon concentration in a superficial layer of the strip has not yet reached an equilibruim level with respect to the time. The method consist of carburization concentration distribution (S7), on the basis of the carburization conditions including given specification data for the steel plate, furnace temperature and composition of the atmospheric gas, outputting the concentration of the components of the atmospheric gas, feed and discharge rates and other carburization conditions when the set carburization rate and an actual carburization rate are equal (S8-S15), and correcting the set carburization rate when a difference between the set carburization rate and an actual carburization rate is large, and correcting the strip feed rate while correcting the composition of the atmospheric gas when a difference between the predetermined carburization rate and set carburization rate is large (S9).