An air flow measurement device includes a first channel plate, a second channel plate facing the first channel plate, a pillar fixing the second channel plate with respect to the first channel plate so as to form a space of a given size between the first channel plate and the second channel plate, a slanted channel formed in the space which is configured to become narrower toward a center portion of the air flow measurement device, a branching passage arranged in the center portion which communicates with the slanted channel, a projection provided in the branching passage so as to partly narrow the branching passage, and an air flow sensor provided in the space. The air flow sensor is arranged at a position higher than a junction between the branching passage and the slanted channel.