A composite manufacturing apparatus includes a width determining mechanism and a gas supplier. The width determining mechanism has a body and a gas passage. The body has a path configured to allow a tape material including fibers impregnated with a resin to pass therethrough. The path has a bottom surface and a pair of wall surfaces. The pair of the wall surfaces form a gap that gradually decreases. The gas passage is provided inside the body and formed by the bottom surface having a plurality of through holes, and is in communication with the plurality of through holes. The gas supplier is configured to supply gas to the gas pass age.