We succeeded in high resolution force measurements by using a noncontact ultrahigh vacuum-atomic force microscope (UHV-AFM) with frequency modulation (FM) detection. We clearly observed adatoms and corner holes on the Si(111)7 x 7 reconstructed surface. Then we applied the noncontact UHV-AFM with FM detection to the high resolution measurement of the electrostatic force. We prevented deterioration of the spatial resolution of the topography by isolating the electrostatic interaction from van der Waals interaction. By simultaneous measurements of the topography and electrostatic force on a silicon oxide, a spatial resolution similar to 15 Angstrom of the electrostatic force was achieved.