Diamond film produced by chemical vapor deposition (CVD) is being used in the electronics industry because of its excellent properties. In order to measure the adhesive strength of CVD diamond, external load is directly applied in a scanning electron microscope to the CVD diamond particles which sparsely appear on silicon substrate in the early stage of deposition. These particles are called nuclei when they are small and grow into contact with each other to form polycrystalline CVD diamond film. Diamond film was supposed to adhere to the substrate at only these discrete nucleation points, which might result in weak adhesive strength. We measure the maximum load, as the adhesive fracture resistance, required to scratch off the particles with 2–13 μm diameter. Adhesive fracture resistance is found to increase with the diameter of the particle. Hence we conclude that CVD diamond does not adhere only at the nucleation points but that the whole contact area to the substrate is responsible for its adhesive strength.