Time correction method of the OTP device is registered in the authentication server by the unique number of OTP device on the basis of the authentication server, the time correction step (S11) for generating a variable time and the allowable range variable, OTP device generates an authentication number and Authentication transmitting the code generation time, and authentication code to the OTP authentication server through the terminal (S12) and, OTP authentication server poison the time correction variables stored in the OTP authentication server based on the unique number shipping step (S13) of the OTP device and, OTP authentication server comprising: by the time tolerances variables stored in the OTP server based on the unique number estimating the time tolerance of the OTP device (S14) and, OTP authentication server allows the current time and the time range of variables in the OTP device and a step (S15) that is based to estimate the minimum time value and a maximum time value of OPT authentication server and to calculate the corrected time value of the OTP device based on the time correction parameters, OTP authentication server is a calibration time value of the OTP device correcting a time value of the OTP authentication server OTP device at least greater than the time value or equal in this OTP determines whether the authentication server up to less than or equal to the time value of the (S16) and a correction time values ​​in the above table at step S16 OTP device the OTP authentication server, at least greater than the time value or equal to the corrected time value of the OTP device is stored in the storage area of ​​the OTP authentication server less than or equal to the maximum time value of the OTP authentication server corresponding to the time correction parameter in the OTP device-specific number and (S17) to end.