A wireless network accessing method adaptable to a portable electronic device is provided. The wireless network accessing method includes following steps. A wireless access point (WAP) is connected. An authentication webpage is received from the WAP. A layout of the authentication webpage is analyzed by using a database to find out an account field and a password field of the authentication webpage. An account and a password input by a user are received. The account field filled with the account and the password field filled with the password are sent to the WAP.