Provided is a fragmentation tip, an intraocular surgery device, a method for suppressing an occurrence of cavitation, and a cataract surgery method, which can suppress the occurrence of cavitation. The fragmentation tip, which is attached to an intraocular surgery device configured to apply ultrasonic vibration, includes: a cylindrical support portion configured to be mounted on the intraocular surgery device; and a cylindrical tip body provided at a distal end of the support portion to be in communication with an internal space of the support portion, wherein the tip body has a cross sectional shape having a length in a first direction that is larger than a length in a second direction that is orthogonal to the first direction, and vibration is applied to the support portion so that the tip body rotates back and forth about an axis of the tip body that passes through its center in the first and second directions.