To provide a ceramic substrate having a break line, in which the occurrence of a crack due to the break line is suppressed when handled before divided, and which is easily divided by the break line during the division.

The ceramic substrate 1 is formed by press working of a ceramic green sheet and is provided with break lines 2 comprising V-shaped grooves that form a 20-40 angle in the cross section. The depth of the grooves configuring the break lines 2 is 3-25% of the thickness of the substrate, wherein the cross section of the bottom of the grooves is formed to a shape having a width of 5 m and of a non-acute angle. Further, it is desirable that the width (W1) of the cross section at the top opening of the groove is 20-500 m and that the ratio (W2/W1) of the width (W2) of the cross section at the bottom of the groove relative to W1 is made 0.25-0.5.