A whole determination area of a targeted wafer is concentrically divided in a radial direction, COP density is obtained in each divided determination segment, a maximum value of the COP density is set as COP densityRADIUSMAX, a minimum value of the COP density is set as COP densityRADIUSMIN, a value computed by “(COP densityRADIUSMAX-COP densityRADIUSMIN)/COP densityRADIUSMAX” is compared to a predetermined set value, and a non-crystal-induced COP and a crystal-induced COP are distinguished from each other based on a clear criterion, thereby determining the COP generation factor. Therefore, a rejected wafer in which a determination of the crystal-induced COP is made despite being the non-crystal-induced COP can be relieved, so that a wafer production yield can be enhanced.