1. A scanning type charged particle beam microscope comprising: a charged particle imaging unit having a charged particle beam irradiation unit to irradiate a focused charged particle beam to a surface of a sample formed with a pattern and to scan it over the surface, and a secondary charged particle imaging unit to detect secondary charged particles emitted from the sample as the charged particle beam irradiation unit irradiates and scans the charged particle beam over the sample and to generate a secondary charged particle image of the sample surface; an image quality improving unit to process the secondary charged particle image of the sample surface generated by the charged particle imaging unit; and an output unit to output a result of processing by the image quality improving unit; wherein the image quality improving unit aligns the position of the design data of the pattern formed on the sample with the position of the secondary charged particle image of the sample surface generated by the charged particle imaging unit and then improves a quality of the secondary charged particle image of the sample surface by using the design data of the pattern formed on the sample.