A security authentication method for a membership login of an online website by use of a security authentication server , the security authentication method comprising: receive a request for a security authentication for a membership login of an online website from a user terminal ; generating (SI00) one-time use authentication information in the form of a QR code image in response to the received request; transmitting (SI00) the generated one-time use authentication information to the user terminal for display on a screen of the user terminal in the form of the QR code image for scanning and analyzing by a smartphone ; receiving (S200) a request for one-time password information from a security authentication related application installed on the smartphone , the request including the analyzed one-time use authentication information and actual membership login authentication information of the online website; verifying (S300) the one-time use authentication information and the actual membership login authentication information of the online website; generating (S300) one-time password information if a corresponding user is an authenticated member; transmitting (S300) the generated one-time password information to the smartphone for display to a user and for input by the user to the user terminal ; receiving (S400) a request for a security authentication for the membership login of the online website from the user terminal , the request including the one-time password information and the one-time use authentication information; and performing (S500) a verification process on the security authentication for the membership login of the online website, and if the user is a security authenticated member, normally processing the membership login of the online website. receive a request for a security authentication for a membership login of an online website from a user terminal ; generating (SI00) one-time use authentication information in the form of a QR code image in response to the received request; transmitting (SI00) the generated one-time use authentication information to the user terminal for display on a screen of the user terminal in the form of the QR code image for scanning and analyzing by a smartphone ; receiving (S200) a request for one-time password information from a security authentication related application installed on the smartphone , the request including the analyzed one-time use authentication information and actual membership login authentication information of the online website; verifying (S300) the one-time use authentication information and the actual membership login authentication information of the online website; generating (S300) one-time password information if a corresponding user is an authenticated member; transmitting (S300) the generated one-time password information to the smartphone for display to a user and for input by the user to the user terminal ; receiving (S400) a request for a security authentication for the membership login of the online website from the user terminal , the request including the one-time password information and the one-time use authentication information; and performing (S500) a verification process on the security authentication for the membership login of the online website, and if the user is a security authenticated member, normally processing the membership login of the online website. <EOS>