a method of collecting impurities existing on the surface of a semiconductor wafer and in a thin film formed on the semiconductor wafer is provided with a process for dripping collecting liquid on the surface of the semiconductor wafer to which hydrophobic processing is applied , a process for elongating the collecting liquid dripped and turned spherical by surface tension in a direction of the radius of the semiconductor wafer with the surface tension kept , a process for relatively rolling and scanning the elongated collecting liquid , touching the collecting liquid to the surface of the semiconductor wafer and incorporating impurities into the collecting liquid , a process for restoring the elongated collecting liquid to the original spherical shape after the impurities are incorporated and a process for withdrawing the collecting liquid restored to the spherical shape from the surface of the semiconductor wafer .