To eliminate the need of inserting an oscillator or a phacofragmentation device into an eyeball in order to crush the lens, and to eliminate the need of incising the cornea or anterior capsule in order to crush the lens.

An oscillation surface 2a of a piezoelectric oscillator 2 is formed into a concave shape and is configured such that ultrasonic waves are converged to a lens 13. Thus, a phacofragmentation device 1 can crush the lens 13 in a state of being arranged outside an eyeball without being inserted into the eyeball. Thus, the need of inserting the oscillator or the phacofragmentation device into the eyeball in order to crush the lens 13 is eliminated, and the need of incising a cornea 11 or an anterior capsule 14 in order to crush the lens 13 is also eliminated.