1. A defect observation method comprising: an imaging process for imaging an inspection object on the basis of defect information from an inspection device and obtaining a defect image and a reference image corresponding to the defect image; a parameter determination process for determining a first parameter to be used in defect extraction by using first feature quantity distribution obtained from the defect image picked up in the imaging process and the reference image and second feature quantity distribution obtained from the reference image; and an observation process for conducting observation by using the first parameter determined in the parameter determination process.