A hydrogen generating device for generating a gas containing hydrogen by decomposing a fuel containing an organic compound, comprising: (a) a partition membrane; (b) a fuel electrode provided on one surface of the partition membrane; (c) means for supplying a fuel containing the organic compound and water to the fuel electrode; (d) an oxidizing electrode provided on the other surface of the partition membrane; (e) means for supplying an oxidizing agent to the oxidizing electrode; (f) means for generating and collecting the gas containing hydrogen from the fuel electrode, (g) a gas diffusion layer formed on the oxidizing electrode; (h) another gas diffusion layer formed on the fuel electrode; (i) a first region including a masking part masking a part of the gas diffusion layer of the oxidizing electrode and a non-masking part not masking a part of the another gas diffusion layer of the fuel electrode, the non-masking part facing the masking part at a corresponding position thereof over the partition membrane; (j) a second region that the masking part is absent both (B, A) on the gas diffusion layer of the oxidizing electrode and the another gas diffusion layer of the fuel electrode at another corresponding position thereof over the partition membrane, (k) a third region wherein the oxidizing electrode is without mask and the fuel electrode is with mask, the non-masking part facing the masking part at a corresponding position thereof over the partition membrane; and (l) a fourth region including the masking part of the gas diffusion layer of the oxidizing electrode and another masking part masking a part of the another gas diffusion layer of the fuel electrode, the masking part of the gas diffusion layer of the oxidizing electrode facing the another masking part of the another gas diffusion layer of the fuel electrode, (m)wherein the masking part on the gas diffusion layer of the oxidizing electrode is a low oxidizing agent supply region where supply of the oxidizing agent is substantially lower than a part that the masking part is absent. (a) a partition membrane; (b) a fuel electrode provided on one surface of the partition membrane; (c) means for supplying a fuel containing the organic compound and water to the fuel electrode; (d) an oxidizing electrode provided on the other surface of the partition membrane; (e) means for supplying an oxidizing agent to the oxidizing electrode; (f) means for generating and collecting the gas containing hydrogen from the fuel electrode, (g) a gas diffusion layer formed on the oxidizing electrode; (h) another gas diffusion layer formed on the fuel electrode; (i) a first region including a masking part masking a part of the gas diffusion layer of the oxidizing electrode and a non-masking part not masking a part of the another gas diffusion layer of the fuel electrode, the non-masking part facing the masking part at a corresponding position thereof over the partition membrane; (j) a second region that the masking part is absent both (B, A) on the gas diffusion layer of the oxidizing electrode and the another gas diffusion layer of the fuel electrode at another corresponding position thereof over the partition membrane, (k) a third region wherein the oxidizing electrode is without mask and the fuel electrode is with mask, the non-masking part facing the masking part at a corresponding position thereof over the partition membrane; and (l) a fourth region including the masking part of the gas diffusion layer of the oxidizing electrode and another masking part masking a part of the another gas diffusion layer of the fuel electrode, the masking part of the gas diffusion layer of the oxidizing electrode facing the another masking part of the another gas diffusion layer of the fuel electrode, (m)wherein the masking part on the gas diffusion layer of the oxidizing electrode is a low oxidizing agent supply region where supply of the oxidizing agent is substantially lower than a part that the masking part is absent.