A method of finding a cluster in a data stream includes updating statistical distribution information of a grid-cell corresponding to a currently generated data element, statistical distribution information on previously generated data elements being managed using grid-cells, which are partitioned within the range of a data space and have statistical distribution information of data elements within the range; comparing the occurrence frequency of the data element in the grid-cell according to the update result with a predefined partitioning threshold, partitioning the grid-cell into a plurality of grid-cells according to the comparison result, and estimating statistical distribution information of the partitioned grid-cells; recursively performing the updating or comparing step until the grid-cell becomes a unit grid-cell; and comparing the occurrence frequency of a data element in the unit grid-cell with a predefined minimum support and defining a set of unit grid-cells as a cluster according to the comparison result.