To obtain a thermal flowmeter that is accurate, is highly durable, and is easily capable of signal processing.

A groove section 12 where fluid flows is formed at a substrate 11, a piezoelectric plate 14 having piezoelectric characteristics is joined to the groove section 12, and comb-shaped electrodes 15, 16, and 17 and a laser light absorption film 18 are formed on the upper surface of the piezoelectric plate 14. In the measurement of flow rate, when a laser beam is applied to the laser light absorption film 18 of the piezoelectric plate 14, for example, for specific time, a temperature change curve where cooling by the mass flow rate of fluid is applied results, so that the oscillation frequency of the piezoelectric plate 14 also follows the curve and changes, and the flow rate is measured based on the temperature change characteristics.