A circuit board (2) includes an insulation layer (7) where a via conductor (10) is embedded. The via conductor (10) includes: a first conductor portion (10a) having an lower portion narrower than an upper portion; and a second conductor portion (10b) which is formed immediately below the first conductor portion (10a), connected to the first conductor portion (10a), and has a maximum width greater than the upper end width of the first conductor portion (10a). The insulation layer (7) has a plurality of indentations (T1a, T1b) on the surface in contact with the via conductor (10). Convex portions (T2a, T2b) of the via conductor are arranged in the indentations (T1a, T1b).