PURPOSE: To enable easy confirmation of the depth of a V-groove to be formed by discriminating the prepreg layer with colors.

CONSTITUTION: On both sides of a layer 1a formed of a prepreg of glass cloth group which is absorbing and being coated with an epoxy resin not including a coloring agent, a layer 2 consisting of a prepreg of glass cloth group which is absorbing and being coated with an epoxy resin including a coloring agent is laminated respectively and these are made into one body. A layer 1b is formed of a prepreg of glass cloth group which is absorbing and being coated with an epoxy resin not including a coloring agent and is laminated unitarily on said layer 2. A layer 3 is a circuit pattern formed on the layer 1b unitarily. In case of a printed wiring substrate constituted as above, when V-grooves for separation are formed oppositely on both sides, for example for multilateral beveling, it is easy to form a desired separation V-groove 4 by referring to the colored prepreg layer 2 which is enclosed in the laminated layers as the standard of the depth of the V-groove.