A manufacturing method of a slinger to be used in a rotary seal that includes the slinger, a core metal, and a seal member, the slinger including a cylindrical sleeve and a flange extending outward in a radial direction from one end of the sleeve in an axial direction, the core metal including a core metal cylinder having a cylindrical shape, and a core metal flange extending inward in the radial direction from one end of the core metal cylinder in the axial direction, the seal member including a base portion joined to the core metal, and a seal lip portion extending from the base portion, the seal lip portion including an axial lip in slidable contact with a first slide-contact surface that is an inner surface of the flange of the slinger, and a radial lip (4C,4D) in slidable contact with a second slide-contact surface that is an outer circumferential surface of the sleeve of the slinger, the manufacturing method comprising: molding an annular blank material from a dull-finished steel sheet material through sheet metal press working, laser cutting machining, or wire cut electric discharge machining; and burring the annular blank material, so as to mold the slinger, wherein the burring is performed using a mold having faces (5A,5B) each of which has an arithmetical mean roughness Ra set to 0.03 μm ≤ Ra ≤ 0.07 μm, the faces (5A,5B) individually coming into contact with the first slide-contact surface and the second slide-contact surface, a ratio of pressure application force for holding the annular blank material between the faces to a 0.2% proof stress of the dull-finished material, is set to 1.0 or more and 1.53 or less, a clearance for the mold used for the burring is set to T × (0.9 to 0.7) where "T" represents a sheet thickness of the annular blank material, and, with these conditions, an arithmetical mean roughness Ra of each of the first slide-contact surface and the second slide-contact surface of the slinger falls within a predetermined range of 0.25 μm ≤ Ra ≤ 0.5 μm. the slinger including a cylindrical sleeve and a flange extending outward in a radial direction from one end of the sleeve in an axial direction, the core metal including a core metal cylinder having a cylindrical shape, and a core metal flange extending inward in the radial direction from one end of the core metal cylinder in the axial direction, the seal member including a base portion joined to the core metal, and a seal lip portion extending from the base portion, the seal lip portion including an axial lip in slidable contact with a first slide-contact surface that is an inner surface of the flange of the slinger, and a radial lip (4C,4D) in slidable contact with a second slide-contact surface that is an outer circumferential surface of the sleeve of the slinger, the manufacturing method comprising: molding an annular blank material from a dull-finished steel sheet material through sheet metal press working, laser cutting machining, or wire cut electric discharge machining; and burring the annular blank material, so as to mold the slinger, wherein molding an annular blank material from a dull-finished steel sheet material through sheet metal press working, laser cutting machining, or wire cut electric discharge machining; and burring the annular blank material, so as to mold the slinger, wherein the burring is performed using a mold having faces (5A,5B) each of which has an arithmetical mean roughness Ra set to 0.03 μm ≤ Ra ≤ 0.07 μm, the faces (5A,5B) individually coming into contact with the first slide-contact surface and the second slide-contact surface, a ratio of pressure application force for holding the annular blank material between the faces to a 0.2% proof stress of the dull-finished material, is set to 1.0 or more and 1.53 or less, a clearance for the mold used for the burring is set to T × (0.9 to 0.7) where "T" represents a sheet thickness of the annular blank material, and,