A digital probing type atomic force microscope (AFM) for measuring high aspect structures with high precision. A probe 21 is vibrated while moved to the vicinity of an atomic force region on a specimen surface. The position of the probe is measured when a specified atomic force is detected in the atomic force region. The probe is then moved away from the specimen surface. A servo system for maintaining a gap between the probe and specimen surface is stopped. The probe is moved to a measurement point along the specimen surface while kept away from the specimen. The vibration frequency is a frequency slightly offset from the cantilever resonance point. The atomic force is detected based on the vibration amplitude of the cantilever.