PURPOSE: To enable air flow to be accurately detected by a hot wire sensor even if pulsation occurs, by disposing the hot wire sensor in a bypass path having an outlet either of two intake shells.

CONSTITUTION: Air also flows from an inlet 12 of a bypass path 11, and air flow speed in the bypass path 11 is measured by a hot wire sensor 6 so that air flow in the right side intake shell 2 can be measured. Also, since air flows in the left and right intake shell 2, are equalized to each other by equalizing the opening areas of throttle valves 5, 5, the air flow in the left intake shell can be also measured by the measurement of air flow in the right intake shell 2. Also, air pulsation can be reduced by composing the pulsation in the right intake shell 2 with that in the left one through the pressure of an air path 14 so that errors in the measurement of the hot wire sensor 6 can be reduced.