Abstract: Disclosed herein is an apparatus and method for upgrading firmware using a universal serial bus (USB). In the method, after setting a flag 1 in a nonvolatile memory mounted on the device, a device is booted in a download mode to download and write firmware binary data in the nonvolatile memory. Then, the device is rebooted after setting a flag 2 in the nonvolatile memory, and booted in a general mode after setting a flag 3 in the nonvolatile memory. Then, USB communication between the device and the computer is checked to determine whether the device succeeds in upgrading the firmware. Thus, even a device with no external key can conveniently upgrade the firmware, and even if power is interrupted during download of a new version of firmware binary data, next booting can be safely performed in the download mode, thereby allowing upgrade of the firmware using the USB.