An image forming device, a host device, and connecting methods thereof are provided. The method includes that when the image forming device is connected to the host device through a wired interface, installing a driver program to execute a wireless connection setting program, determining an internet protocol (IP) setting method of the image forming device according to an IP setting method of the host device, copying network setup information of the host device and transmitting the copied network setup information to the image forming device through the wired interface, and when the image forming device sets an IP address thereof according to the determined IP setting method and transmits the IP address to the host device through the wired interface, establishing a wireless connection setting using the transmitted IP address.