A memory device performing an internal copy operation is provided. The memory device may receive a source address, a destination address, and page size information together with an internal copy command, compares the source address with the destination address, and performs an internal copy operation. The internal copy operation may be an internal block copy operation, an inter-bank copy operation, or an internal bank copy operation. The internal copy operation may be performed with respect to one-page data, half-page data, or quarter-page data, based on the page size information. The memory device may output as a flag signal a copy-done signal indicating that the internal copy operation has been completed.