A hinge module according to one embodiment includes a fixed structure including a central portion, a guide portion having an edge facing an edge of the central portion, and a support portion configured to connect the central portion and the guide portion, wherein an interior space is formed between the central portion and the guide portion, a connecting shaft extending into the interior space through the central portion and including a gear formed on at least a part of an outer circumferential surface of the connecting shaft, and a rotary structure disposed in the interior space, the rotary structure including a circular arc shaped gear having a plurality of gear teeth arranged in a circular arc shape and that are engaged with the gear, wherein the rotary structure rotates about a virtual axis of rotation passing through a center of a circular arc of the circular arc shaped gear.