A foldable electronic device comprising: a first housing and a second housing; a hinge structure (200a, 200b) connected to the first housing and the second housing; and a display disposed in the first housing and/or the second housing, wherein the hinge structure includes: a first shaft rotating about a first axis; a second shaft rotating about a second axis; a first arm part connected to the first shaft; a second arm part connected to the second shaft; a first rotation part connected to the first arm part and rotating about a third axis; a second rotation part connected to the second arm part and rotating about a fourth axis; a first main gear (231_2) disposed on the first shaft; a second main gear (232_2) disposed on the second shaft; and characterized by a first compound gear and a second compound gear disposed between the first main gear and the second main gear, wherein the first compound gear includes: a first gear portion (233_1) geared with the first main gear, and of which a distance from a center point of the first gear portion to a gear tooth end of the first gear portion is a first radius; and a second gear portion (233_2) geared with the second compound gear, and of which a distance from a center point of the second gear portion to a gear tooth end of the second gear portion is a second radius that is smaller than the first radius, and wherein the second compound gear includes: a third gear portion (234_1) geared with the second main gear, and of which a distance from a center point of the third gear portion to a gear tooth end of the third gear portion is the first radius; and a fourth gear portion (234_2) geared with the second gear portion of the first compound gear, and of which a distance from a center point of the fourth gear portion to a gear tooth end of the fourth gear portion is the second radius. a first housing and a second housing; a hinge structure (200a, 200b) connected to the first housing and the second housing; and a display disposed in the first housing and/or the second housing, wherein the hinge structure includes: a first shaft rotating about a first axis; a second shaft rotating about a second axis; a first arm part connected to the first shaft; a second arm part connected to the second shaft; a first rotation part connected to the first arm part and rotating about a third axis; a second rotation part connected to the second arm part and rotating about a fourth axis; a first main gear (231_2) disposed on the first shaft; a second main gear (232_2) disposed on the second shaft; and characterized by a first compound gear and a second compound gear disposed between the first main gear and the second main gear, a first shaft rotating about a first axis; a second shaft rotating about a second axis; a first arm part connected to the first shaft; a second arm part connected to the second shaft; a first rotation part connected to the first arm part and rotating about a third axis; a second rotation part connected to the second arm part and rotating about a fourth axis; a first main gear (231_2) disposed on the first shaft; a second main gear (232_2) disposed on the second shaft; and characterized by a first compound gear and a second compound gear disposed between the first main gear and the second main gear, wherein the first compound gear includes: a first gear portion (233_1) geared with the first main gear, and of which a distance from a center point of the first gear portion to a gear tooth end of the first gear portion is a first radius; and a second gear portion (233_2) geared with the second compound gear, and of which a distance from a center point of the second gear portion to a gear tooth end of the second gear portion is a second radius that is smaller than the first radius, and a first gear portion (233_1) geared with the first main gear, and of which a distance from a center point of the first gear portion to a gear tooth end of the first gear portion is a first radius; and a second gear portion (233_2) geared with the second compound gear, and of which a distance from a center point of the second gear portion to a gear tooth end of the second gear portion is a second radius that is smaller than the first radius, and wherein the second compound gear includes: a third gear portion (234_1) geared with the second main gear, and of which a distance from a center point of the third gear portion to a gear tooth end of the third gear portion is the first radius; and a fourth gear portion (234_2) geared with the second gear portion of the first compound gear, and of which a distance from a center point of the fourth gear portion to a gear tooth end of the fourth gear portion is the second radius. a third gear portion (234_1) geared with the second main gear, and of which a distance from a center point of the third gear portion to a gear tooth end of the third gear portion is the first radius; and a fourth gear portion (234_2) geared with the second gear portion of the first compound gear, and of which a distance from a center point of the fourth gear portion to a gear tooth end of the fourth gear portion is the second radius.