Microwave irradiator 12 is attached to a furnace main body of a heating furnace 11 having microwave permeability. A running passage for passing a fiber member F which is the object to be heated is formed inside the heating furnace 11. A first tubular member 13 made of a first microwave heat-generating material absorbing microwave energy and generating heat is rotatably disposed around the running passage. A second tubular member made of a second microwave heat-generating material absorbing microwave energy and generating heat is disposed in the first tubular member 13. The fiber member F is heated and calcined while running the fiber member F containing carbon in the running passage of the second tubular member 14.