1. An individual certification method using a portable telephone, said method comprising the sequentially executed steps of: requesting a unique query code from a certification server, the requesting being performed by a registered user through a portable telephone; verifying the user as a registered user; generating the unique query code on the certification server, the unique query code being a random one-time code uniquely associated with the user request; transmitting the unique query code from the certification server to the user's portable telephone; receiving by the portable telephone the unique query code generated by the certification server; directly and wirelessly transferring the query code from said portable telephone to a sales management server; then returning the query code from said sales management server to the certification server; comparing the generated query code transferred to the portable telephone with the query code transmitted from the sales management server in the certification server for verification; and transmitting user's personal identification information to the sales management server when the two query codes are determined to be identical to each other.