The high heat flux in MEB far exceeding CHF should be considered a result of violent growing and collapsing behavior of coalescent bubbles in that region, which strongly introduces subcooled liquid to the heated surface. This bubble behavior generates a high pressure in the vicinity of the surface. In this study, a measurement of the pressure fluctuation in the liquid near the surface was performed synchronously with a recording of the bubble motion by use of a void probe set close to the surface. In high liquid subcooling conditions (S-MEB I), the void probe signal in the vicinity of the surface shows regular cyclic behavior synchronous with the pressure waveform. Under a medium subcooling condition (S-MEB II), there appear three different modes in the void signal in sequence. The one looks random and does not synchronize with the pressure waveform. The another is very systematic and similar to the signal in high liquid subcooling. The other shows a constant void fraction of a high value, indicating the surface to be covered with a thick vapor blanket. The time fraction of the second mode increases gradually with increasing the heat flux.