SCAN TYPE PROBE MICROSCOPE

PROBLEM TO BE SOLVED: To attain high sensitivity and a wide operation range concerning a scan type probe microscope for detecting the vertical movement of a probe with the use of an optical lever.SOLUTION: A scan type probe microscope includes: a reflection mirror 10b arranged on the upper surface of a cantilever 10c where a probe 10a is arranged on the lower surface; a light beam projector 30 that generates a light beam 36 and allows the light beam to be made incident to the reflection mirror; a split type photodetector 35 having a detection surface that is halved into at least first and second detection surfaces and to which a reflection light beam 37 reflected against the reflection mirror 10b is made incident; and a calculation circuit 58 for outputting a difference of light intensity detected on the first and second detection surfaces as the movement amount of the reflection light beam 37. Reflection light beam 37 has an irradiation pattern 92 for allowing the detection surface 35a of the split type photodetector 35 to be irradiated in a ring shape.