A gas meter apparatus (1) of the present invention comprises a flow measuring device (5) which measures a gas flow; a measurement value calculating section (21) and a liquid crystal display section (2) which are configured to calculate an integrated value of the measured gas flow and electrically display the integrated value. Every time the measurement value calculating section (21) determines that the integrated value has reached 1 liter, it informs a light emission commanding section (22) of determination result. In response to this information, the light emission commanding section (22) causes a LED light emitting section (3) to emit light toward a sensor (7). Therefore, the gas meter apparatus (1) is able to conduct a test by a test method in which a change in the displayed integrated value of the gas flow can be known from reflected light of emitted light, even when the integrated value of the gas flow is displayed in a digital form.