To provide a method of manufacturing a spark plug that can easily obtain a plug structure in which a good heat-transferring layer covers not only an outer circumferential surface but also a leading end of a center layer.

A heat-transferred member 120 for forming a heat-transferring layer 12 includes a first member 121 being coat an outer circumferential surface of a core body 130 for forming a center layer 13 and forming an outer circumferential surface 12a of the heat-transferring layer 12, and a second member 122 being disposed adjacent to a leading end side of the core body 130 and forming a leading end 12b of the heat-transferring layer 12. Plastic forming carried out for cladding by disposing second member 122 adjacently to the leading end side of the core body 130 to make up the center layer 13, whereby it can prevent a leading end face 13b of the center layer 13 from projecting and separating the leading end 12b of the heat-transferring layer 12 and can improve loss of heating and prevent deformation.