A fuel cell including, a cell unit which has a fuel electrode including a
catalyst, an air electrode including a catalyst, and an electrolyte
membrane which is sandwiched by the fuel electrode and the air electrode;
a fuel chamber which is disposed at a fuel electrode side, and which
stores fuel; an air chamber which is disposed at an air electrode side
and to which air is supplied; and a recovery chamber in which a fuel-side
by-product, which is generated by a catalytic reaction of the fuel at the
fuel electrode, is recovered, wherein a colorant containing an indicator
is provided inside of one of the fuel chamber and the recovery chamber.