To detect the clogging of an air suction hole easily.

The clogging detecting device 25 has a vibration generating device 11 which vibrates air passing through an air suction hole 12 in an air sampling pipe 1, and this vibration of air is detected by a vibration detecting device 20 to know if there is clogging. At the current meter, the fluid is vibrated by a vibration generation device 11 mounted in a pipe material in which air flows, the frequency of the generated vibration is detected by the frequency detecting device 20, and the flow speed is estimated from the difference in the detected frequencies.