PURPOSE: To precisely measure the flow rate of air, by dividing an air passage into two subpassages in a part, in the vicinity of a fuel injection valve disposed therein, and by opening both output ports of a bypass passage provided in its intermediate section with a thermal type air-flowmeter, to both two divided subpassages.

CONSTITUTION: A fuel injection valve 14 is supported by a pair of support arms 16 in an air passage 12 formed in a body 10. Further, a throttle valve fixed to a shaft is disposed in the air passage 12 downstream of the valve 14. Meanwhile, a bypass valve 22 is arranged in parallel with the air passage 12, having its inlet port opened to the upstream side of the fuel injection valve 14 and its intermediate part disposed therein with a thermal type air flowmeter 28. In this arrangement, both outlet ports 26A, 26B of the bypass passage 22 are opened respectively to two upstream side air subpassages 32, 34 which are separated by the support arms 16. Further, the outlet ports 26A, 26B are opened at positions spaced by an equal angle from the center of the air passage 12 with respect to the line A-A passing through the support arm 16.