The present disclosure provides an intake air flow rate measuring device. The intake air flow rate measuring device includes a flange, a casing, a flow rate sensor, a humidity sensing element, an element terminal, and a humidity terminal. The humidity terminal is spaced away from the element terminal. A portion of the casing between the element terminal and the humidity terminal is defined as a suppressing portion, and a cross-section of the suppressing portion is defined as a suppressing portion cross-section. An end portion of the casing close to the flange is defined as a base portion, and a cross-section of the base portion is defined as a base portion cross-section. The suppressing portion cross-section is set to be smaller than the base portion cross-section.