A self-rotating flow meter includes a housing, a rotating mechanism and a sensor. The rotating mechanism is disposed in a chamber of the housing between an inlet port and an outlet port. The sensor is disposed in the housing and near the rotating mechanism. The rotation mechanism contains inflow and outflow passages in a rotating shaft and a rotating disk respectively. The inlet flow passage has a centerline that is coincident with or parallel to the centerline of the rotating shaft. The centerline of any outlet flow passage in the rotating disk and the centerline of the rotating shaft are in two different planes and have a distance between them.