To understand fundamentals of kidney stone™s fragmentation by shock wave impingement, experimental approach was carried out. Air gun system was used to transfer a well-controlled stress wave into a thin disk specimen. The specimen was fabricated with plaster and its dimensions are 10 mm in diameter and 1.2 mm in thickness. The obtained results are summarized as follows: As the stress pulse duration is decreased from 12 microseconds to 5 microseconds, the critical stress for fracture increased tremendously. The critical fracture stress for a specimen with a small hole in the specimen center is about one fifth of that for the plain specimen. The fracture takes place along the diameter perpendicular to the stress wave incident direction. Numerical stress analysis suggests that the principal stress criterion can explain the fracture mode.