An operation method of a storage device, which includes a storage controller and a nonvolatile memory device, includes performing first boot-up operation, performing first training on a plurality of data signals such that a detection operation of the first training is repeatedly performed on windows of the data signals, storing offset information generated based on a result of the first training, performing a normal operation based on the result of the first training, performing a second boot-up operation, performing second training on the plurality of data signals based on the offset information generated in the first training such that a detection operation of the second training is repeatedly performed on a left edge section and a right edge section of windows of the data signals, and performing the normal operation based on a result of the second training.