Patent ID: 7891240

Claim:
A thermal type flow measuring device comprising: a sub passage which takes in a portion of a fluid flowing through a main passage; and a sensor element disposed in the sub passage to thereby detect a flow rate of the portion of the fluid, wherein the sub passage has a first sub passage portion formed in a front surface side of a plate-shaped member and curving with no intersection, a second sub passage portion formed on a back surface side of the plate-shaped member and curving with no intersection, and a third sub passage portion formed as an opening which passes through from the front surface side to the back surface side of the plate-shaped member, the first sub passage portion is communicatively connected to one end of the third sub passage portion in a direction along a plate surface of the plate-shaped member, the second sub passage portion is communicatively connected to the other end of the third sub passage portion in the direction along the plate surface of the plate-shaped member, and the sensor element is disposed in the third sub passage portion.