A circuit board includes an insulating substrate having a first surface and a second surface opposite to the first surface, a solid conductor located inside the insulating substrate, a first via conductor connected to the solid conductor from a side of the first surface, and a second via conductor connected to the solid conductor from a side of the second surface. The solid conductor has a cutout that intersects a line segment that connects a node of the first via conductor and a node of the second via conductor to each other.