Disclosed are an apparatus and a method for sensing opening of a current interrupt device (CID) of a battery unit. An apparatus for sensing opening of a current interrupt device of a battery unit according to the present invention is configured to include: a setting unit setting a predetermined voltage section when discharge of one or more battery units starts; a measuring unit measuring a voltage section pass time which is the time when the one or more battery units pass through the predetermined voltage section for each battery unit; and a detecting unit detecting a battery unit in which the current interrupt device (CID) is opened among the one or more battery units and detecting the number of battery cells in which the CID is opened among one or more battery cells included in the battery unit in which the CID is opened based on the voltage section pass time for each battery unit.