To provide a signal detection apparatus enabling simplification of a mechanism for detecting the displacement of a probe and simplification of the arrangement of a detection system even if a plurality of probes are in use, thus enabling a space saving, a scanning atomic force microscope constructed of the detection apparatus, and a signal detection method.

In the signal detection apparatus detecting an atomic force acting between a probe and a sample and measuring the unevenness or electric characteristic of the sample surface from changes in signals, the probe is driven by an electrostatic force working between a plate electrode on the support base of the probe and another plate electrode provided oppositely to the former electrode on the probe and the displacement of the probe is detected from changes in electrostatic capacitance between the electrodes.