FUEL BATTERY CELL, FUEL BATTERY SYSTEM, LEAK DETECTION METHOD

The present invention aims to provide a fuel battery system improved in reliability by accurately detecting when a fuel electrode gas or an air electrode gas has leaked. A fuel battery cell according to the present invention includes a first electrode, an electrolyte membrane, and a second electrode which are layered on a support substrate. Further, at least any one of the first electrode, the electrolyte membrane, and the second electrode is electrically isolated by an insulating member to form a first region and a second region. The insulating member is disposed at a position where the insulating member does not overlap with an opening portion of the support substrate (refer to FIG. ).