Included are removing an outermost layer or outermost layers on one side or both sides of liquid crystal polymer film; and a molding step of performing thermocompression molding on liquid crystal polymer film and metal foil stacked on the side of liquid crystal polymer film whose outermost layer is removed. A heating temperature in the molding step is in a range from a temperature equal to a melting start temperature, of the liquid crystal polymer film, measured by using a rigid body pendulum type viscoelasticity measuring device to a temperature 60° C. higher than the melting start temperature inclusive.