An ultracapacitor comprising: a case (110 ; 210) having a cylindrical shape of which one end is closed and the other end is opened; a bare cell (120 ; 220) placed inside the case (110 ; 210) and shaped like a winding element comprising a positive electrode , a negative electrode and a separator ; a first internal terminal arranged in a closed region of the case (110 ; 210) within the case (110 ; 210) and connected to a positive electrode of the bare cell (120 ; 220); a second internal terminal arranged in an open region of the case (110 ; 210) within the case (110 ; 210) and connected to a negative electrode of the bare cell ; and an external terminal (150 ; 250) connected to the second internal terminal at an outside of the case (110 ; 210), characterized in that each of the first and second internal terminals comprises a case coupling plate (136, 146 ; 236, 246) having a flat bottom surface (136a, 146a ; 236a, 246a) formed with a plurality of electrolyte injection holes (136b, 146b ; 236b, 246b) on a surface thereof, and a lateral surface (136c, 146c ; 236c, 246c) arranged perpendicularly along an outer circumference of the bottom surface (136a, 146a ; 236a, 246a), the bottom surface (136a, 146a ; 236a, 246a) of the case coupling plates (136, 146 ; 236, 246) is in contact with and laser-welded to the bare cell (120 ; 220), and the lateral surface (136c, 146c ; 236c, 246c) of the case coupling plates (136, 146 ; 236, 246) is formed in a flat surface, and the external terminal (150 ; 250) comprises a stepped portion protruding with the width difference at one side, and the case coupling plate (146 ; 246) of the second internal terminal is fitted to the stepped portion . a case (110 ; 210) having a cylindrical shape of which one end is closed and the other end is opened; a bare cell (120 ; 220) placed inside the case (110 ; 210) and shaped like a winding element comprising a positive electrode , a negative electrode and a separator ; a first internal terminal arranged in a closed region of the case (110 ; 210) within the case (110 ; 210) and connected to a positive electrode of the bare cell (120 ; 220); a second internal terminal arranged in an open region of the case (110 ; 210) within the case (110 ; 210) and connected to a negative electrode of the bare cell ; and an external terminal (150 ; 250) connected to the second internal terminal at an outside of the case (110 ; 210), characterized in that each of the first and second internal terminals comprises a case coupling plate (136, 146 ; 236, 246) having a flat bottom surface (136a, 146a ; 236a, 246a) formed with a plurality of electrolyte injection holes (136b, 146b ; 236b, 246b) on a surface thereof, and a lateral surface (136c, 146c ; 236c, 246c) arranged perpendicularly along an outer circumference of the bottom surface (136a, 146a ; 236a, 246a), the bottom surface (136a, 146a ; 236a, 246a) of the case coupling plates (136, 146 ; 236, 246) is in contact with and laser-welded to the bare cell (120 ; 220), and the lateral surface (136c, 146c ; 236c, 246c) of the case coupling plates (136, 146 ; 236, 246) is formed in a flat surface, and the external terminal (150 ; 250) comprises a stepped portion protruding with the width difference at one side, and the case coupling plate (146 ; 246) of the second internal terminal is fitted to the stepped portion . <EOS>