A data scrambling method for controlling a code density according to an exemplary embodiment of the present disclosure includes receiving a plain code which is a code to be stored in the non-volatile memory device and a storage address at which the plain code is recorded; determining a rank corresponding to the plain code, using an ET table including appearance frequency rank information corresponding to individual plain code; calculating an adjustment rank corresponding to the plain code, using the rank and a random number that is generated based on the address of storage address; determining a cipher code corresponding to the appearance frequency rank of the plain code, using the adjustment rank and an ECC table including rank information determined by an objective function for individual cipher code; and storing the cipher code in the storage address.