A gas sensor device is equipped with the sensor cell, the pump cell, the inner void space, and the gas inlet. The sensor cell is created by a portion of the solid electrolyte body and a pair of sensor electrodes disposed on the solid electrolyte body. The pump cell is created by a portion of the solid electrolyte body and a pair of pump electrodes disposed on the solid electrolyte body. The inner void space faces the sensor electrode and the pump electrode. If a dimension of said gas inlet in a direction in which the measurement gas flows in the gas inlet is defined as L1, a sectional area of the gas inlet taken perpendicular to the direction of flow of the measurement gas in the gas inlet is defined as S1, a distance between the gas inlet and the sensor cell is defined as L2, and a sectional area of the inner void space taken perpendicular to a direction in which the pump cell and the sensor cell are aligned with each other is defined as S2, a relation of 1000≤(L1/S1)×(L2/S2)≤5000 is met.