A scanning probe microscope has a cantilever having: a probe that is to be contacted or approached on a surface of a sample; and a processor that operates to perform a process including: calculating a measurement width MW and an offset value OV from a minimum value Smin and a maximum value Smax of a signal indicating a displacement of the cantilever with the following Equations (1) and (2) when a prescanning operation is performed before the measurement data is acquired by the probe microscope controller; and adjusting at least one of the offset value OV and the measurement width MW based on a temporal variation of the signal at the same position on the surface of the sample when the prescanning operation is performed. MW=(Smax−Smin)  Equation (1) OV=(MW/2)+Smin  Equation (2)