A thermal flowmeter having a thin film part formed on a substrate and a heater resistor disposed on the thin film part for measuring the flow rate of a fluid, comprising: a first temperature difference sensor (9, 10) disposed upstream of the heater resistor in the flowing direction of the fluid to be measured and a second temperature difference sensor (11, 12) disposed downstream of the heater resistor in the flowing direction of the fluid to be measured; a first heating temperature sensor disposed upstream of the first temperature difference sensor (9, 10) and a second heating temperature sensor disposed downstream of the second temperature difference sensor (11, 12), wherein the first temperature difference sensor (9, 10) comprises a first temperature sensing resistor and a second temperature sensing resistor, and the second temperature difference sensor (11, 12) comprises a third temperature sensing resistor and a fourth temperature sensing resistor; the thermal flow meter further comprising: a fifth temperature sensing resistor disposed at a position on the substrate distant from the thin film part to detect the temperature of the fluid; a detection means for measuring the flow rate of the fluid according to the difference between the temperatures detected by the first temperature difference sensor (9, 10) and the second temperature difference sensor (11, 12), wherein the detection means comprises a bridge circuit formed by connecting a series circuit constituted of the first temperature sensing resistor and the third temperature sensing resistor in parallel with a series circuit constituted of the second temperature sensing resistor and the fourth temperature sensing resistor, wherein the detection means detects the flow rate of the fluid according to the differential voltage from the bridge circuit; and heating control means for controlling the heating current to be supplied to the heater resistor, wherein the heating control means comprises a bridge circuit formed by connecting a series circuit constituted of the first heating temperature sensor, the second heating temperature sensor, and a resistor in parallel with a series circuit constituted of the fifth temperature sensing resistor and a resistor, wherein the heating control means is adapted to detect the differential voltage from the bridge circuit for controlling the current to be applied to the heater resistor, wherein the heating control means is adapted to control the heating current to be supplied to the heater resistor such that the average temperature of the temperatures measured by the first heating temperature sensor and the second heating temperature sensor settles to be higher by a predetermined temperature than the temperature of the fluid which temperature is detected by the fifth temperature sensing resistor. a first temperature difference sensor (9, 10) disposed upstream of the heater resistor in the flowing direction of the fluid to be measured and a second temperature difference sensor (11, 12) disposed downstream of the heater resistor in the flowing direction of the fluid to be measured; a fifth temperature sensing resistor disposed at a position on the substrate distant from the thin film part to detect the temperature of the fluid; a detection means for measuring the flow rate of the fluid according to the difference between the temperatures detected by the first temperature difference sensor (9, 10) and the second temperature difference sensor (11, 12), wherein the detection means comprises a bridge circuit formed by connecting a series circuit constituted of the first temperature sensing resistor and the third temperature sensing resistor in parallel with a series circuit constituted of the second temperature sensing resistor and the fourth temperature sensing resistor, wherein the detection means detects the flow rate of the fluid according to the differential voltage from the bridge circuit; and heating control means for controlling the heating current to be supplied to the heater resistor, wherein the heating control means comprises a bridge circuit formed by connecting a series circuit constituted of the first heating temperature sensor, the second heating temperature sensor, and a resistor in parallel with a series circuit constituted of the fifth temperature sensing resistor and a resistor, wherein the heating control means is adapted to detect the differential voltage from the bridge circuit for controlling the current to be applied to the heater resistor,