A thermal type flow measuring apparatus comprising: a fixed temperature difference bridge circuit for controlling current flowing through a heat generating resistor, wherein a flow rate of a fluid is detected by using an upstream-side temperature sensor and a downstream-side temperature sensor which are arranged on the upstream and downstream side of the heat generating resistor, wherein the fixed temperature difference bridge circuit consists of a first serially connected circuit in which the heat generating resistor as the first temperature sensitive resistor and a second temperature sensitive resistor are connected in series and a second serially connected circuit in which a third temperature sensitive resistor and a fourth temperature sensitive resistor are connected in series, and the first serially connected circuit and the second serially connected circuit are connected in parallel by connecting one end of the first temperature sensitive resistor and one end of the third temperature sensitive resistor, and connecting one end of the second temperature sensitive resistor and one end of the fourth temperature sensitive resistor, characterized in that the first, second, third and fourth temperature sensitive resistors are formed on a semiconductor base plate, and the first temperature sensitive resistor is formed on a thin wall portion formed in the semiconductor base plate together with the flow rate measuring temperature sensors, wherein the second, third and fourth temperature sensitive resistors are formed outside of the thin wall portion, wherein the first, second, third and forth temperature sensitive resistors (10 - 13) have the same resistance-temperature coefficient, and wherein the second temperature sensitive resistor and the fourth temperature sensitive resistor are arranged close to each other in order that the second temperature sensitive resistor and the fourth temperature sensitive resistor are held at the same temperature, or wherein the third temperature sensitive resistor and the fourth temperature sensitive resistor are arranged close to each other in order that the third temperature sensitive resistor and the fourth temperature sensitive resistor are held at the same temperature. a fixed temperature difference bridge circuit for controlling current flowing through a heat generating resistor, wherein a flow rate of a fluid is detected by using an upstream-side temperature sensor and a downstream-side temperature sensor which are arranged on the upstream and downstream side of the heat generating resistor, wherein the fixed temperature difference bridge circuit consists of a first serially connected circuit in which the heat generating resistor as the first temperature sensitive resistor and a second temperature sensitive resistor are connected in series and a second serially connected circuit in which a third temperature sensitive resistor and a fourth temperature sensitive resistor are connected in series, and the first serially connected circuit and the second serially connected circuit are connected in parallel by connecting one end of the first temperature sensitive resistor and one end of the third temperature sensitive resistor, and connecting one end of the second temperature sensitive resistor and one end of the fourth temperature sensitive resistor, the first, second, third and fourth temperature sensitive resistors are formed on a semiconductor base plate, and the first temperature sensitive resistor is formed on a thin wall portion formed in the semiconductor base plate together with the flow rate measuring temperature sensors, wherein the second, third and fourth temperature sensitive resistors are formed outside of the thin wall portion, wherein the first, second, third and forth temperature sensitive resistors (10 - 13) have the same resistance-temperature coefficient, and wherein the second temperature sensitive resistor and the fourth temperature sensitive resistor are arranged close to each other in order that the second temperature sensitive resistor and the fourth temperature sensitive resistor are held at the same temperature, or wherein the third temperature sensitive resistor and the fourth temperature sensitive resistor are arranged close to each other in order that the third temperature sensitive resistor and the fourth temperature sensitive resistor are held at the same temperature.