A head-mounted device, comprising: a main frame couplable to an electronic device; and a support part configured to affix the main frame to a facial side of the user; and an auxiliary input device including: a body; an input module disposed on at least one surface of the body and configured to process an input signal for controlling a function of the electronic device; a sensor module disposed in the body and configured to obtain sensing information in accordance with a movement of the auxiliary input device; and a connection part electrically connectable to the electronic device and configured to serve as a path through which the input signal and the sensing information are transmitted to the electronic device, wherein the auxiliary input device further comprises an extension part disposed between the body and the connection part, having a connection circuit line connecting the input module to an electrical connection part of the connection part, and wherein the extension part is fixed to a moving member formed in one surface of the body to allow the extension part to move with respect to the body, wherein the moving member is inserted into a hole, the hole formed in the at least one surface of the body to have a length and a width, wherein one end of the moving member inserted in the hole is stuck in the hole, such that the moving member may move in a longitudinal direction of the hole without being separated from the hole, and wherein the hole is formed in at least one of a vertical direction and a horizontal direction on the at least one surface of the body to have the length. a main frame couplable to an electronic device; and a support part configured to affix the main frame to a facial side of the user; and an auxiliary input device including: a body; an input module disposed on at least one surface of the body and configured to process an input signal for controlling a function of the electronic device; a sensor module disposed in the body and configured to obtain sensing information in accordance with a movement of the auxiliary input device; and a connection part electrically connectable to the electronic device and configured to serve as a path through which the input signal and the sensing information are transmitted to the electronic device, wherein the auxiliary input device further comprises an extension part disposed between the body and the connection part, having a connection circuit line connecting the input module to an electrical connection part of the connection part, and wherein the extension part is fixed to a moving member formed in one surface of the body to allow the extension part to move with respect to the body, wherein the moving member is inserted into a hole, the hole formed in the at least one surface of the body to have a length and a width, wherein one end of the moving member inserted in the hole is stuck in the hole, such that the moving member may move in a longitudinal direction of the hole without being separated from the hole, and wherein the hole is formed in at least one of a vertical direction and a horizontal direction on the at least one surface of the body to have the length. a body; an input module disposed on at least one surface of the body and configured to process an input signal for controlling a function of the electronic device; a sensor module disposed in the body and configured to obtain sensing information in accordance with a movement of the auxiliary input device; and a connection part electrically connectable to the electronic device and configured to serve as a path through which the input signal and the sensing information are transmitted to the electronic device, wherein the auxiliary input device further comprises an extension part disposed between the body and the connection part, having a connection circuit line connecting the input module to an electrical connection part of the connection part, and wherein the extension part is fixed to a moving member formed in one surface of the body to allow the extension part to move with respect to the body, wherein the moving member is inserted into a hole, the hole formed in the at least one surface of the body to have a length and a width, wherein one end of the moving member inserted in the hole is stuck in the hole, such that the moving member may move in a longitudinal direction of the hole without being separated from the hole, and wherein the hole is formed in at least one of a vertical direction and a horizontal direction on the at least one surface of the body to have the length.