There is provided a dimensionally accurate insulating substrate in which plane direction-wise shrinkage is practically zero and shrinkage variations are small. The insulating substrate includes a laminated body composed of at least two kinds of insulating layers made of crystallizable glass ceramics. The crystallization temperature of crystallizable glass contained in the first insulating layer is lower than the softening point of crystallizable glass contained in the second insulating layer. The difference in thermal expansion coefficient between the first and second insulating layers is preferably 2.times.10.sup.-6/.degree. C. or below.