In recent days, although many kinds of beam modifiers are developing and using for clinical purposes in accordance with progressing medical engineering, physical wedges are preferred to use as a beam modifier by a lot of institutions until now because of cost, complexities of dosimetry and mechanical uncertainties. According to progressing technology, available field size of wedge is more enlarger than that of old model LINAC. Because field size dependence of wedged fields increases in new model LINAC, we was trying to know that how much different PSFs are in enlarged wedged fields compared with open fields. In small or middle size of fields($4{ imes}4{sim}15{ imes}15cm$), there are only a few percents of PSF variation between open and wedged fields. But there are $2{sim}8\%;variations;in;relatively;large;fields(20{ imes}20{sim}30{ imes}40cm).$