Provided is a method of shaping a composite blade made of a composite material by curing prepreg in which reinforcing fibers are impregnated with resin. A foaming agent disposed in an internal space of the composite blade contains a plurality of foaming bodies and foaming agent resin. The foaming bodies foam by being heated. The foaming agent resin cures by being heated. The foaming bodies include low-temperature side foaming bodies and high-temperature side foaming bodies. The low-temperature side foaming bodies foam in a low temperature range during a curing step. The high-temperature side foaming bodies foam in a high temperature range corresponding to temperatures higher than the low temperature range during the curing step.