Abstract: A turbo fan, formed by ultrasonic welding, a first component including: a flat portion; and plate-shaped blade portions standing from the flat portion, and a second component having recessed groove portions in each of which an end portion of the respective blade portion fits. The groove portions have a groove width greater than a thickness of the end portions of the blade portions. The turbo fan includes a group of positioning ribs partially burying two clearances created on two sides of the end portion in a thickness direction thereof, respectively, in a pre-welding state. The group of positioning ribs protrude in the thickness direction from the end portion of at least one of the blade portions, or from side surfaces of at least one of the groove portions, and are in contact with side surfaces of the groove portion, or in contact with the end portion of the blade portion.