Provided is a technology which creates an autorun file that is used in autorun for preventing the autorun of a USB-based portable storage, thereby allowing an arbitrary user or worm virus not to manipulate the autorun file. A method for preventing autorun of portable storage accesses at least one of a master file table entry of a root directory and a master file table entry of an autorun file, and sets non-autorun in the at least one accessed master file table entry.