A control device authentication method in a home network system which includes a slave, a home server which controls the slave, and the control device which performs a remote control function to control the home server, includes registering the control device to the home server; generating and storing, by the control device and the home server, a one-way function set; storing, by the control device and the home server, a code value of a button pressed at the control device; creating, by the control device, a first password by performing an operation using a pointer value, the code value, and a one-way function number; requesting, by the control device, authentication by transferring the pointer value, the one-way function number, and the first password to the home server; and creating, by the home server, a second password.