A flow rate meter has (i) a housing therein defines a bypass path in which a part of the main flow flows, and (ii) a flow rate sensor that is arranged in the bypass path. The housing has a sidewall arranged to extend along a main flow direction. The bypass path has, as an outlet, a through-hole that is defined in the sidewall. The flow rate meter further has a plate member that is arranged to face the sidewall and defines a space into which a part of the main flow flowing outside of the housing flows. The plate member is arranged parallel with the sidewall and intersects with a center line that is perpendicular to the main flow direction and passes through a center of the through-hole.