A memory system includes a memory device including plural memory blocks storing plural pieces of data classified by a first attribute and a second attribute different from the first attribute, and a controller configured to determine whether each data stored in each page in a first part of a target memory block for garbage collection in the memory device has either the first attribute or the second attribute, to determine that all data stored in a second part of the memory block has one of the first attribute and the second attribute, based on a first attribute page count of the memory block and the number of pages storing data of the first attribute in the first part of the memory block, and to migrate data having one of the first attribute and the second attribute to another memory block.