A method of writing data in a storage device including sequentially receiving a plurality of data write commands, sequentially assigning a plurality of write data corresponding to the plurality of data write commands to a plurality of buffer groups by determining continuity of logical addresses of the plurality of write data such that each of the plurality of buffer groups temporarily stores some of the plurality of write data included in a respective single stream and having consecutive logical addresses, assigning a plurality of serial numbers to the plurality of write data, respectively, based on an order in which the plurality of write data are assigned to the plurality of buffer groups, programming the plurality of write data temporarily stored in the plurality of buffer groups into a plurality of memory blocks, and updating a logical-to-physical mapping table based on the plurality of serial numbers may be provided.