To provide a testing apparatus for a gas analytical device by which a series of operations from a readout operation of test data obtained from each gas analyzer up to the creation of a test result certificate can be performed in a short time, even when an output specification is changed to a current output from a voltage output and by which an artificial mistake can be prevented.

The gas analytical device 1 is provided with a plurality of gas analyzes 2, 3 whose measuring objects are different. In the testing apparatus for the gas analytical device, corresponding calibration gases are supplied to the gas analyzers 2, 3; a prescribed calculation is performed on the basis of the test data D obtained at the gas analyzers 2, 3, whether the gas analytical device 1 is good or not is judged; and the test result certificate is created automatically. The testing apparatus is provided with a data converter 4 which sets an optimum range for a calibration so as to match the output specification of the gas analyzers 2, 3, and which A/D-converters an output data signal A; and a computer 11 to which the A/D-converted test data D is input so as to be read out, by which the prescribed calculation is performed, which judges whether the gas analytical device is good or not, and by which the test result certificate is created.