The present invention provides a multi-layer disk recordingreproducing apparatus that records information on a multi-layer disk having a plurality of recording layers or reproduces the information from the multi-layer disk. Each of the level shift circuits is formed of a common electrical element and an electrical element connected to the common electrical element. A wavelength displacement amount of the monochromatic beam is calculated, using a forward voltage value corresponding to the constant current, and a forward voltage initial value. The shield assembly alternately covers and exposes the electrode assembly to the electric field.