The present invention relates to an ultracapacitor comprising: a cylindrically-shaped case having one end closed and the other end open; a wound element-type bare cell disposed inside the case and having a positive electrode, a negative electrode, and a separator; a first inner terminal disposed inside the case in an enclosed region of the case and connected to the positive electrode of the bare cell; a second inner terminal disposed inside the case in an open region of the case and connected to the negative electrode of the bare cell; and an outer terminal connected to the second inner terminal on the outside of the case, wherein the sides of the first inner terminal and the second inner terminal form a flat surface and when coupled with the case, the first and second inner terminals are coupled with the case through a constricting process.