The scintillation properties and radiation durability of β-SiAlON:Eu were evaluated under focused microbeam irradiation conditions using 3 MeV protons. In situ observation of scintillation from β-SiAlON:Eu was monitored using ion-beam-induced luminescence (IBIL) and compared with that from ZnS:Ag scintillators. A comparison of the spectra of IBIL from both scintillators shows that the intensity of IBIL was analogous at different peak wavelengths of 545 nm for β-SiAlON:Eu and 450 nm for ZnS:Ag under the same irradiation conditions. Better radiation hardness towards focused proton microbeam irradiation was observed for the β-SiAlON:Eu scintillator when continuous measurements by IBIL were used. A decay constant of approximately 1.11 × 1016, which is two orders of magnitude higher than that for ZnS:Ag, was obtained for the β-SiAlON:Eu scintillator for focused proton microbeam irradiation. IBIL was also capable of visualizing a previously damaged area of a ZnS:Ag scintillator, which corresponds to the focused beam scanning area of 100 × 100 μm2. Meanwhile, the irradiated region was not significantly distinguishable from the nonirradiated region on the β-SiAlON:Eu scintillator under the same beam fluence. These results suggest that β-SiAlON:Eu could be an ideal candidate scintillator for convenient ionized particle beam monitoring and a diagnostic tool for focused and intense beam fluence conditions up to 1016 ions/cm2.