To provide a method for forming break grooves onto a ceramic aggregate substance, in which the break grooves having a proper shape can be formed in the proper positions even in the deformed and shrunk ceramic aggregate substrate.

Such a pattern is printed in a ceramic green sheet, in which a plurality of circuits are printed, that straight lines capable of dividing the circuits are decided. The deformed and shrunk ceramic aggregate substrate 20 are obtained by burning the ceramic green sheet. The positions of the patterns 12 on the ceramic aggregate substrate 20 are deviated from the positions corresponding to the straight lines in corresponding to deformation and shrinkage. Accordingly, damage of the circuits caused by break grooves 22 can be prevented by forming the break grooves 22 for dividing the circuits along the patterns 12 on the ceramic aggregate substrate 20.