A circuit board includes an insulating layer including first and second insulator films, a first wiring layer embedded in the first insulator film and including pads and first wiring patterns exposed from the first insulator film, and a second wiring layer including second wiring patterns formed on the second insulator film and via wirings penetrating the insulating layer and electrically connecting the second wiring patterns to the first wiring layer. The first insulator film is made of a reinforcement-free resin that includes no reinforcing member. The second insulator film is made of a reinforcing member impregnated with a resin.