A method of manufacturing a heat sink according to one aspect of the present disclosure is a method of manufacturing a heat sink including a base material having a surface on which a heat-radiation resin-coated film is formed, the method comprising: taking the base material out of a die-casting mold after the base material is die-cast; and forming the heat-radiation resin-coated film on the surface of the base material using residual heat of the base material taken out of the die-casting mold. In forming the heat-radiation resin-coated film, the heat-radiation resin-coated film is formed on the surface of the base material by bonding a heat-radiation resin film to the surface of the base material.