Experiment of unsteady pressure measurement on the surface of wing with 75° sweep delta wing has been carried out in a wind tunnel in order to investigate unsteady characteristics of breakdown vortices over delta wing after the leading edge vortices were breakdown. The result of experiment shows that alter of RMS pressure fluctuations and fluid state of leading edge vortices on the top surface of delta wing are correlative. At the angle region with vortex breakdown, RMS of pressure fluctuations are very huge, similarly buffeting strength of delta wing are large. With increasing angle of attack, alter of buffeting strength is in accordance with RMS pressure fluctuations. Analysis of the pressure signal shows the spiral wave of the breakdown vortex flow over the wing is the primary part of whole RMS pressure fluctuations. Delta wing produces buffeting because of the spiral wave.