A user authentication method by using an authentication virtual code, the method comprising: receiving, by a virtual code verifying means, the authentication virtual code, wherein the authentication virtual code is generated by an authentication virtual code generating function included in a virtual code generating means registered in the virtual code verifying means; wherein the virtual code includes a first code, a second code and a third code, the first code equals to a generation time code plus a one time password, OTP, the OTP is a virtual security code generated, by the virtual code generating means, based on an authentication virtual code available time when a user is capable of employing the authentication virtual code set by authority, the second code equals to the first code minus a user identification, UID, or sub-identification, SID, and the third code equals to the generation time code; wherein the generation time code is associated with a point in time when the virtual authentication virtual code is generated, searching, by the virtual code verifying means, for a storage location of the user identification, UID, or the sub-identification, SID, based on the first and the second codes; extracting, by the virtual code verifying means, authority information stored in the storage location of the found UID or SID; verifying, by the virtual code verifying means, the authentication virtual code based on a time point at which the authentication virtual code is received by: generating, by the virtual code verifying means, an OTP within a specific count range from the time point at which a user authentication virtual code is received based on the storage location, and determining whether there is a code, in the generated OTP, identical to the virtual security code included in the authentication virtual code, calculating, by the virtual code verifying means, data regarding the authentication virtual code available time from the virtual security code and a difference between the calculated time data and the generation time data included in the third code; and performing, by the virtual code verifying means, user authentication based on the extracted authority information only when the difference is within a preset range. receiving, by a virtual code verifying means, the authentication virtual code, wherein the authentication virtual code is generated by an authentication virtual code generating function included in a virtual code generating means registered in the virtual code verifying means; wherein the virtual code includes a first code, a second code and a third code, the first code equals to a generation time code plus a one time password, OTP, the OTP is a virtual security code generated, by the virtual code generating means, based on an authentication virtual code available time when a user is capable of employing the authentication virtual code set by authority, the second code equals to the first code minus a user identification, UID, or sub-identification, SID, and the third code equals to the generation time code; wherein the generation time code is associated with a point in time when the virtual authentication virtual code is generated, searching, by the virtual code verifying means, for a storage location of the user identification, UID, or the sub-identification, SID, based on the first and the second codes; extracting, by the virtual code verifying means, authority information stored in the storage location of the found UID or SID; verifying, by the virtual code verifying means, the authentication virtual code based on a time point at which the authentication virtual code is received by: generating, by the virtual code verifying means, an OTP within a specific count range from the time point at which a user authentication virtual code is received based on the storage location, and determining whether there is a code, in the generated OTP, identical to the virtual security code included in the authentication virtual code, calculating, by the virtual code verifying means, data regarding the authentication virtual code available time from the virtual security code and a difference between the calculated time data and the generation time data included in the third code; and performing, by the virtual code verifying means, user authentication based on the extracted authority information only when the difference is within a preset range. generating, by the virtual code verifying means, an OTP within a specific count range from the time point at which a user authentication virtual code is received based on the storage location, and determining whether there is a code, in the generated OTP, identical to the virtual security code included in the authentication virtual code, calculating, by the virtual code verifying means, data regarding the authentication virtual code available time from the virtual security code and a difference between the calculated time data and the generation time data included in the third code; and performing, by the virtual code verifying means, user authentication based on the extracted authority information only when the difference is within a preset range.