A gas instrument determiner section included in a flow meter device determines whether or not a gas instrument in use is a fuel cell, by comparing an actual measurement value of a gas flow measured at first measurement time intervals in a first determination operation period from when inflowing of the gas starts until a predetermined time lapses, to determination flow data, and by comparing an actual measurement value measured at second measurement time intervals longer than the first measurement time interval in a second determination operation period which ends after the first determination operation period ends, to determination flow data. This makes it possible to accurately determine the gas instrument in use even when the gas instrument in use is the fuel cell.