A method for forming protrusions to form one or more protrusions on one or more surfaces of a metal workpiece, the method comprising: clamping and fixing the metal workpiece (1, 7, 10, 26, 32, 54) between a support die (2, 27, 33, 56) and a pressure die (3, 28, 34, 57); pressing end cross sections of outer peripheral end parts (5, 30, 37) of the metal workpiece (1, 7, 10, 26, 32, 54) fixed between the support die (2, 27, 33, 56) and the pressure die (3, 28, 34, 57) from two or more directions perpendicular or oblique to an upright direction of the protrusions to be formed on one surface of the metal workpiece by press molding using a pressing die or a pressing jig that is furnished separately from the support die (2, 27, 33, 56) and the pressure die (3, 28, 34, 57), wherein two or more positions on end cross sections of outer peripheral end parts (5, 9, 30, 37) of the metal workpiece (1, 7, 10, 26, 32, 54) are pressed from two or more directions toward the protrusion to be formed on one surface of the metal workpiece (1, 7, 10, 26, 32, 54) and wherein the two or more positions thereon are located in the two or more directions that are positioned in point symmetry from a center of a bottom surface of the protrusion to be formed; undergoing plastic flows of the metal of the metal workpiece (1, 7, 10, 26, 32, 54) into one or more through holes formed in a at least one of the support die and the pressure die as one or more recessed parts that are formed as female molds for forming the protrusions (6, 31, 38, 58); and forming one or more solid protrusions (6, 31, 38, 58) on the surfaces of the metal workpiece (1, 7, 10, 26, 32, 54), characterized by the pressing being performed at a temperature lower than a softening point of a metal used as the metal workpiece (1, 7, 10, 26, 32, 54) without heating the metal workpiece (1, 7, 10, 26, 32, 54), and by undergoing plastic flows of the unheated metal of the metal workpiece (1, 7, 10, 12, 26, 32, 54) into one or more through-holes (4, 29, 35, 55) formed as the recessed parts in at least one of the support die (2, 27, 33, 56) and the pressure die (3, 28, 34, 57) in combination of moving each of the two or more positions on end cross sections of outer peripheral end parts (5, 9, 11, 30, 37) of the metal workpiece (1, 7, 10, 26, 32, 54) toward the through-holes by the pressing. clamping and fixing the metal workpiece (1, 7, 10, 26, 32, 54) between a support die (2, 27, 33, 56) and a pressure die (3, 28, 34, 57); pressing end cross sections of outer peripheral end parts (5, 30, 37) of the metal workpiece (1, 7, 10, 26, 32, 54) fixed between the support die (2, 27, 33, 56) and the pressure die (3, 28, 34, 57) from two or more directions perpendicular or oblique to an upright direction of the protrusions to be formed on one surface of the metal workpiece by press molding using a pressing die or a pressing jig that is furnished separately from the support die (2, 27, 33, 56) and the pressure die (3, 28, 34, 57), wherein two or more positions on end cross sections of outer peripheral end parts (5, 9, 30, 37) of the metal workpiece (1, 7, 10, 26, 32, 54) are pressed from two or more directions toward the protrusion to be formed on one surface of the metal workpiece (1, 7, 10, 26, 32, 54) and wherein the two or more positions thereon are located in the two or more directions that are positioned in point symmetry from a center of a bottom surface of the protrusion to be formed; undergoing plastic flows of the metal of the metal workpiece (1, 7, 10, 26, 32, 54) into one or more through holes formed in a at least one of the support die and the pressure die as one or more recessed parts that are formed as female molds for forming the protrusions (6, 31, 38, 58); and forming one or more solid protrusions (6, 31, 38, 58) on the surfaces of the metal workpiece (1, 7, 10, 26, 32, 54), characterized by the pressing being performed at a temperature lower than a softening point of a metal used as the metal workpiece (1, 7, 10, 26, 32, 54) without heating the metal workpiece (1, 7, 10, 26, 32, 54), and by undergoing plastic flows of the unheated metal of the metal workpiece (1, 7, 10, 12, 26, 32, 54) into one or more through-holes (4, 29, 35, 55) formed as the recessed parts in at least one of the support die (2, 27, 33, 56) and the pressure die (3, 28, 34, 57) in combination of moving each of the two or more positions on end cross sections of outer peripheral end parts (5, 9, 11, 30, 37) of the metal workpiece (1, 7, 10, 26, 32, 54) toward the through-holes by the pressing.