An air flow measuring device, comprising: a body with a main air passage; and a sensor attached to the body for detecting a flow rate of air passing through the main air passage, and a positioning part including a portion on the body and a portion on the sensor for positioning the body and the sensor, wherein the portion of the positioning part being provided on the body is positioned outside a projected area of the sensor in viewing the body in an insertion direction of the sensor, and wherein the body has an attachment surface to which the sensor is attached, and wherein the positioning part has a protrusion which protrudes from the body to a position higher than the attachment surface to be opposed to a part of the sensor in attaching the sensor, thereby restricting movement of the sensor in a plane direction along the attachment surface, and wherein the positioning part includes a body fitting portion including the protrusion, and a sensor fitting portion adapted to be fitted into the body fitting portion by attaching the sensor to the body, and wherein the sensor fitting portion includes an end edge of the sensor opposed to the protrusion, and wherein an attachment hole through which a fixation screw is inserted is formed in the sensor, wherein a screw hole into which the fixation screw is screwed is formed in the body, characterized in that the protrusion has an arc-shaped inner wall surface whose center is located in a coaxial position with respect to a center of the screw hole, and wherein the end edge has an outer wall surface in an arc shape whose center is located in a coaxial position with respect to a center of the attachment hole, the outer wall surface being opposed to the inner wall surface by attaching the sensor to the body. a body with a main air passage; and a sensor attached to the body for detecting a flow rate of air passing through the main air passage, and a positioning part including a portion on the body and a portion on the sensor for positioning the body and the sensor, wherein the portion of the positioning part being provided on the body is positioned outside a projected area of the sensor in viewing the body in an insertion direction of the sensor, and wherein the body has an attachment surface to which the sensor is attached, and wherein the positioning part has a protrusion which protrudes from the body to a position higher than the attachment surface to be opposed to a part of the sensor in attaching the sensor, thereby restricting movement of the sensor in a plane direction along the attachment surface, and wherein the positioning part includes a body fitting portion including the protrusion, and a sensor fitting portion adapted to be fitted into the body fitting portion by attaching the sensor to the body, and wherein the sensor fitting portion includes an end edge of the sensor opposed to the protrusion, and wherein an attachment hole through which a fixation screw is inserted is formed in the sensor, wherein a screw hole into which the fixation screw is screwed is formed in the body, characterized in that the protrusion has an arc-shaped inner wall surface whose center is located in a coaxial position with respect to a center of the screw hole, and wherein the end edge has an outer wall surface in an arc shape whose center is located in a coaxial position with respect to a center of the attachment hole, the outer wall surface being opposed to the inner wall surface by attaching the sensor to the body.