Battery cell including stepped structure

The present invention relates to a battery cell, provided in a battery case, having an electrode assembly of a structure having a separation film interposed between an anode and a cathode. Provided is the battery cell comprising: the battery case composed of an upper case and a lower case, wherein the upper case has a first receiving part and the lower case has a second receiving part for holding the electrode assembly, and the first part and the second part have different sizes structurally; and the electrode assembly formed in an external shape corresponding to the inner shapes of the first receiving part and the second receiving part.