A manufacturing method of a ceramic electronic device includes forming a multilayer structure by stacking a plurality of stack units, each of the stack units having a structure in which a pattern of metal conductive paste is provided on a dielectric green sheet including a dielectric material, the metal conductive paste including a metallic material of which a main component is Ni and a co-material of which a main component is barium titanate, the metal conductive paste of each of the stack units being alternately shifted, and firing the multilayer structure. FWHM of the metallic material)/(FWHM of the co-material) is 0.550 or less. The FWHM is of a (111) face evaluated by powder X-ray diffraction. An average particle diameter of the metallic material before the firing is 120 nm or less.