We report experimental measurements of the field distribution of the light spot focused by a two-dimensional photonic crystal flat lens at wavelengths 1.51–1.58 μm. The photonic crystal slab is fabricated on a silicon-on-insulator substrate by focused-ion-beam direct milling. We confirm the light focusing by the photonic crystal slab through direct observation of the light spot entering into free space at the end facet of the slab lens. The beam profiles as the function of lateral position are measured and the minimal full width half maximum of the beam at 1.2 μm (0.77λ) is obtained.