A flow measurement device, comprising: a flow sensor including a heater configured to heat the measurement target fluid and a temperature sensor (111, 112) configured to sense a temperature of the measurement target fluid, the heater and the temperature sensor (111, 112) being arranged parallel to each other and being further arranged in a flow direction of the measurement target fluid, the flow sensor being configured to sense a flow rate of a measurement target fluid flowing through a main channel; a characteristic-value obtaining unit including a second heater configured to heat the measurement target fluid and a second temperature sensor (121, 122) configured to sense a temperature of the measurement target fluid, the characteristic-value obtaining unit being configured to obtain a characteristic value of the measurement target fluid; a flow rate correction unit configured to correct a flow rate of the measurement target fluid calculated based on a sensing signal output from the flow sensor using the characteristic value of the measurement target fluid obtained by the characteristic-value obtaining unit, and a sub-channel section branching from the main channel and having one end continuous with a first inlet (34a, 34A) opening in the main channel and another end continuous with a first outlet (35a, 35A) opening in the main channel, the sub-channel section including a characteristic-value sensing channel containing the second temperature sensor (121, 122) included in the characteristic-value obtaining unit, wherein the second heater and the second temperature sensor (121, 122) are arranged parallel to each other and are further arranged in a direction orthogonal to a flow direction of the measurement target fluid, wherein the flow sensor is at a position different from the characteristic-value sensing channel, the sub-channel section further includes a flow sensing channel containing the flow sensor, characterized in that the flow sensing channel and the characteristic-value sensing channel are defined by the sub-channel section and are separated by a circuit board located in parallel with the flow direction of the measurement target fluid in the sub-channel section or the channel branching from the sub-channel section, the characteristic-value obtaining unit obtains the characteristic value based on a difference between the temperatures of the measurement target fluid sensed by the second temperature sensor (121, 122) before and after a temperature of the second heater is changed, and the flow sensor is located on a first surface of the circuit board and the second temperature sensor (121, 122) included in the characteristic-value obtaining unit is located on a second surface of the circuit board opposite to the first surface. a flow sensor including a heater configured to heat the measurement target fluid and a temperature sensor (111, 112) configured to sense a temperature of the measurement target fluid, the heater and the temperature sensor (111, 112) being arranged parallel to each other and being further arranged in a flow direction of the measurement target fluid, the flow sensor being configured to sense a flow rate of a measurement target fluid flowing through a main channel; a characteristic-value obtaining unit including a second heater configured to heat the measurement target fluid and a second temperature sensor (121, 122) configured to sense a temperature of the measurement target fluid, the characteristic-value obtaining unit being configured to obtain a characteristic value of the measurement target fluid; a flow rate correction unit configured to correct a flow rate of the measurement target fluid calculated based on a sensing signal output from the flow sensor using the characteristic value of the measurement target fluid obtained by the characteristic-value obtaining unit, and a sub-channel section branching from the main channel and having one end continuous with a first inlet (34a, 34A) opening in the main channel and another end continuous with a first outlet (35a, 35A) opening in the main channel, the sub-channel section including a characteristic-value sensing channel containing the second temperature sensor (121, 122) included in the characteristic-value obtaining unit, wherein the second heater and the second temperature sensor (121, 122) are arranged parallel to each other and are further arranged in a direction orthogonal to a flow direction of the measurement target fluid, wherein the flow sensor is at a position different from the characteristic-value sensing channel, the sub-channel section further includes a flow sensing channel containing the flow sensor, characterized in that the flow sensing channel and the characteristic-value sensing channel are defined by the sub-channel section and are separated by a circuit board located in parallel with the flow direction of the measurement target fluid in the sub-channel section or the channel branching from the sub-channel section, the characteristic-value obtaining unit obtains the characteristic value based on a difference between the temperatures of the measurement target fluid sensed by the second temperature sensor (121, 122) before and after a temperature of the second heater is changed, and the flow sensor is located on a first surface of the circuit board and the second temperature sensor (121, 122) included in the characteristic-value obtaining unit is located on a second surface of the circuit board opposite to the first surface.