A conductance at an oxidizer flow path forming member is defined as C1, a conductance at an opening portion of the oxidizer flow path forming member at which an oxidizer flow rate regulating portion is arranged is defined as C2, the conductances have a relationship of C1>C2. Further, the fuel cell stack has at least one inner fuel cell unit having a value of C1/C2 which is larger than values of C1/C2 of fuel cell units located at both ends of the fuel cell stack.