An apparatus for measuring electric characteristics of a semiconductor includes a light irradiating means for irradiating light to a characteristic measured semiconductor, an alternating-current voltage source, an electric potential measuring means and an impedance regulator wherein impedance is regulated by an impedance regulator in such a manner that electric potential at an electric potential measuring point of the characteristic measured semiconductor may become zero electric potential in the state in which light is not irradiated on the characteristic measured semiconductor by the light irradiating means. Electric characteristics of the characteristic measured semiconductor are measured based on measurement of electric potential obtained with or without irradiation of light onto the characteristic measured semiconductor. With this arrangement, semiconductor electric characteristics can be measured with high accuracy by a simple arrangement.