A flow rate measuring device has a flow channel including: a pair of first and second centrifugal chambers each having a curved wall surface; a first guiding flow channel allowing a first secondary flow channel to communicate with one end of the wall surface of the first centrifugal chamber; an intermediate flow channel allowing the other end of the wall surface of the first centrifugal chamber to communicate with one end of the wall surface of the second centrifugal chamber; a second guiding flow channel allowing the other end of the wall surface of the second centrifugal chamber to communicate with a second secondary flow channel; a first flow dividing channel communicating with the first centrifugal chamber a second flow dividing channel communicating with the second centrifugal chamber; and a detection space portion, in which a detection element is placed.