An optical fiber is provided which has good laser beam condensation efficiency and is highly resilient, and a shockwave generating device employing same. An optical fiber is employed in an underwater shockwave generating device which projects a laser beam underwater and generates an underwater shockwave. The optical fiber includes a main body part, and a laser convergence part that is disposed upon a leading end thereof. The laser convergence part is configured so as to exhibit an approximately frustum shape wherein the diameter of the leading end is narrower than the diameter of the base end, and such that an interior angle with respect to a radial direction of a lateral face of an axial cross-section gradually decreases toward the front thereof.