1. An encryption method comprising: an encryption step of encrypting an object code; an encryption result judgment step of judging whether a new code having a value within a predetermined range is generated as the result of encrypting the object code into an encrypted object code in said encryption step; an encryption result confirmation step which, in case said encryption result judgment step judges that a new code having a value within the predetermined range is not generated, confirms the encrypted object code as an encryption result of the object code; and a re-encryption step which, in case said encryption result judgment step judges that a new code having a value within the predetermined range is generated, re-encrypts the encrypted object code by performing the same encryption process as said encryption step.