The validity of the idea of severity near the notch root of notched FRP plates is investigated experimentally. The investigation was accomplished by obtaining experimental data on the static and cyclic loading tests for notched plates of a glass fiber-reinforced polypropylene (GF/PP). To evaluate the damage near the notch root, we measured the luminance distributions by means of a luminance-measuring technique using a CCD camera. The experimental results for the static loading tests show that the configuration and the area of damaged zone near the notch root were determined by both the maximum elastic stress at the notch root, σmax and notch-root radius ρ. The maximum elastic stress at fracture, σmax,c is governed by the notch-root radius ρ and it is independent of notch depth. The number of loading cycles to fatigue damage initiation is determined by both the σmax and ρ. These experimental results confirm the validity of the failure criterion in static load and the fatigue failure criterion based on the idea of severity near the notch root.