Air flow meter

An air flow meter is provided with a housing having a sub-passage and a circuit chamber, and a flow rate detection sensor. The flow rate detection sensor includes a diaphragm having a flow rate detection portion formed on a main surface, a recessed portion formed on a back surface side of the diaphragm, and a sealing portion having a first sealing portion and a second sealing portion, the first sealing portion being disposed in the sub-passage, and the second sealing portion being disposed in the circuit chamber. A ventilation passage connected to the recessed portion is formed inside the sealing portion, the recessed portion communicates with the sub-passage via a plurality of ventilation paths, and the plurality of ventilation paths communicate with the sub-passage via the ventilation passage. 空气流量计具备具有副通路和电路室的壳体以及流量检测传感器。流量检测传感器具有在主面上形成有流量检测部的隔膜、在隔膜的背面侧形成的凹部、以及具有第一封装部和第二封装部的封装部，第一封装部配置在副通路中，第二封装部配置在电路室中。在封装部的内部形成有与凹部连接的通气通路，凹部经由多个换气路径与副通路连通，多个换气路径经由通气通路与副通路连通。