A network authentication method using a card device includes the following steps: (A) after a user terminal executes an application that is successfully authenticated, the user terminal is connected to a server via the executed application, and a server verification request is sent to the card device; (B) when the server verification request is received, the card device generates a server dynamic link program according to a server authentication code; (C) the user terminal transmits a server dynamic link program to the server via the executed application; (D) the server generates server code data, and transmits the server code data to the user terminal; (E) the user terminal sends the server code data to the card device via the executed application; and (F) and the card device judges whether the server code data satisfies the server authentication code.