n endoscope device comprising: an endoscope including an insertion portion and a first balloon attached to a distal end of the insertion portion; an insertion guide that is to be covered on the insertion portion to guide insertion of the insertion portion, the insertion guide comprising a second balloon on its distal end and having an outer diameter larger than those of the insertion portion; and a balloon controller that controls air pressures of the first and second balloons (60, 80), wherein the insertion portion or the insertion guide is fixed in a body cavity by expanding the first balloon or the second balloon with the balloon controller, respectively, wherein the balloon controller controls the air pressures of the first and second balloons (60, 80) so that the first balloon and the second balloon are substantially equal to each other in size when they are expanded, wherein the first balloon and the second balloon are fixed to be substantially equal to each other in friction resistance against the body cavity when they are expanded, wherein the first balloon and the second balloon comprise materials that are substantially equal to each other in friction resistance against the body cavity, and the first balloon and the second balloon are equal to each other in coefficient of expansion, and characterized in that the balloon controller is adapted to supply air to each of the first and second balloons to expand each of the first and second balloons, and to keep an expanded state of each of the first and second balloons by controlling the air pressures thereof at constant values, the balloon controller is adapted to suck the air from each of the first and second balloons to contract each of the first and second balloons, and to keep a contracted state of each of the first and second balloons by controlling the air pressures thereof at constant values, and the balloon controller is adapted to control the air pressures of the first and second balloons (60, 80) to a same supplied pressure so that the first balloon and the second balloon are kept with the substantially same size. an endoscope including an insertion portion and a first balloon attached to a distal end of the insertion portion; an insertion guide that is to be covered on the insertion portion to guide insertion of the insertion portion, the insertion guide comprising a second balloon on its distal end and having an outer diameter larger than those of the insertion portion; and a balloon controller that controls air pressures of the first and second balloons (60, 80), wherein the insertion portion or the insertion guide is fixed in a body cavity by expanding the first balloon or the second balloon with the balloon controller, respectively, wherein the balloon controller controls the air pressures of the first and second balloons (60, 80) so that the first balloon and the second balloon are substantially equal to each other in size when they are expanded, wherein the first balloon and the second balloon are fixed to be substantially equal to each other in friction resistance against the body cavity when they are expanded, wherein the first balloon and the second balloon comprise materials that are substantially equal to each other in friction resistance against the body cavity, and the first balloon and the second balloon are equal to each other in coefficient of expansion, and characterized in that the balloon controller is adapted to supply air to each of the first and second balloons to expand each of the first and second balloons, and to keep an expanded state of each of the first and second balloons by controlling the air pressures thereof at constant values, the balloon controller is adapted to suck the air from each of the first and second balloons to contract each of the first and second balloons, and to keep a contracted state of each of the first and second balloons by controlling the air pressures thereof at constant values, and the balloon controller is adapted to control the air pressures of the first and second balloons (60, 80) to a same supplied pressure so that the first balloon and the second balloon are kept with the substantially same size.