A roof for an electric furnace, comprising: a seating port of annular shape that has a ceiling seating surface disposed horizontally and a ceiling support surface that extends from an inner circumferential edge of the ceiling seating surface inwards and downwards reducing a diameter of the ceiling support surface from a top thereof to a bottom; a large ceiling including: an upper roof panel that encloses the ceiling seating port and radially extends from the ceiling seating port at a downward inclination angle; a lower roof panel disposed below the upper roof panel at a position spaced apart from the upper roof panel by a predetermined distance; and a side roof panel connected to an extension edge of the upper roof panel and to an extension edge of the lower roof panel to enclose the extension edges of the upper and lower roof panels (132, 134), wherein the upper roof panel is connected to an outer circumferential surface of the ceiling seating port, and wherein the lower roof panel is connected to a lower end of the ceiling support surface to increase the inclination angle of the lower roof panel; and a small ceiling that is seated into the seating port, wherein a shell is provided enclosing an outer circumferential surface of the small ceiling and is brought into close contact with the ceiling support surface, and wherein stop protrusions are provided on the shell and are placed on the ceiling seating surface. a seating port of annular shape that has a ceiling seating surface disposed horizontally and a ceiling support surface that extends from an inner circumferential edge of the ceiling seating surface inwards and downwards reducing a diameter of the ceiling support surface from a top thereof to a bottom; a large ceiling including: an upper roof panel that encloses the ceiling seating port and radially extends from the ceiling seating port at a downward inclination angle; a lower roof panel disposed below the upper roof panel at a position spaced apart from the upper roof panel by a predetermined distance; and a side roof panel connected to an extension edge of the upper roof panel and to an extension edge of the lower roof panel to enclose the extension edges of the upper and lower roof panels (132, 134), an upper roof panel that encloses the ceiling seating port and radially extends from the ceiling seating port at a downward inclination angle; a lower roof panel disposed below the upper roof panel at a position spaced apart from the upper roof panel by a predetermined distance; and a side roof panel connected to an extension edge of the upper roof panel and to an extension edge of the lower roof panel to enclose the extension edges of the upper and lower roof panels (132, 134), wherein the upper roof panel is connected to an outer circumferential surface of the ceiling seating port, and wherein the lower roof panel is connected to a lower end of the ceiling support surface to increase the inclination angle of the lower roof panel; and a small ceiling that is seated into the seating port, wherein a shell is provided enclosing an outer circumferential surface of the small ceiling and is brought into close contact with the ceiling support surface, and wherein stop protrusions are provided on the shell and are placed on the ceiling seating surface.