To provide a small flow-rate measuring device by which a flow rate can be detected with high accuracy irrespective of the flow direction of a fluid.

A heating resistor 30 is set at a reference temperature which is higher than that of an intake-temperature detecting body 20 by a fixed temperature. A flow- rate detecting body 21 is arranged and installed on the upstream side from the heating resistor 30 with respect to the forward direction of an intake flow. The heating resistor 30 is bent in a plurality of numbers of times so as to be at right angles to the direction of the intake flow, and it has a prescribed width in the direction of the intake flow. As a result, heat is hardly transmitted to the direction of the intake flow of the heating resistor 30. When the upstream part of the intake flow of the heating resistor 30 is cooled by the intake flow and when the temperature in the upstream part of the intake flow becomes lower than the reference temperature, the temperature in the downstream part of the intake flow becomes higher than the reference temperature so that the temperature of the heating resistor 30 can be kept at the reference temperature. When the direction of the intake flow is reversed, also the temperature distribution of the heating resistor 30 is reversed. Consequently, when the temperature of the flow-rate detecting body 21 is compared with the reference temperature, the amount of the intake flow and the direction of the intake flow can be detected.