A circuit board includes an insulating member and a semiconductor chip encapsulated with the thermoplastic resin portion of the insulating member. A wiring member is located in the insulating member and electrically connected to first and second electrodes on respective sides of the semiconductor chip. The wiring member includes a pad, an interlayer connection member, and a connection portion. A diffusion layer is located between the first electrode and the connection portion, between the pad and the connection portion, and between the second electrode and the interlayer connection member. At least one element of the interlayer connection member has a melting point lower than a glass-transition point of the thermoplastic resin portion. The connection portion is made of material having a melting point higher than a melting point of the thermoplastic resin portion.