Method for manufacturing wiring substrate, and wiring substrate

A method for manufacturing a wiring substrate, comprising:

• forming a laminate comprising a core substrate, a first build-up part, and a second build-up part;
• forming a first groove on the laminate from a surface of the laminate on a first build-up part side such that the first groove is formed in the first build-up part;
• forming a second groove on the laminate from a surface of the laminate on a second build-up part side such that the second groove is formed in the second build-up part and has a center of a width that is offset from a center of a width of the first groove;
• and
• cutting the core substrate in the laminate along one of the first groove in the first build-up part and the second groove in the second build-up part such that the laminate is divided into a plurality of wiring substrates,
• wherein the laminate is formed such that the first build-up part is formed on a first surface of the core substrate and that the second build-up part is formed on a second surface of the core substrate on an opposite side with respect to the first surface of the core substrate.