An air flow rate measuring device is provided in which a pressure loss across a grid therein due to the load which is generated when a hose band is tightened is reduced and deterioration of its measurement accuracy due to the grid deformation is prevented. The grid is configured to have a grid portion which absorbs deformation at the outer periphery thereof, and another grid portion which does not absorb deformation at the inner periphery thereof. In order to make the grid portions independent of each other, the grid is provided with a frame, and the mesh grid inside of the frame which maintains a rectifying effect, prevents the deterioration of the measurement accuracy, and does not absorb deformation, and the grid outside of the frame absorbs deformation.