A wireless IC device (101) includes a resin member (70) including a first surface (VS1) and a second surface (VS2), a substrate (1) including a first principal surface (PS1) and a second principal surface (PS2), a coil antenna provided in the resin member (70), and an RFIC element (61) mounted on the substrate (1) and connected to the coil antenna. The substrate (1) is embedded in the resin member (70) so that the second principal surface (PS2) is at the second-surface-(VS2) side. The coil antenna is formed of first linear conductor patterns (20A to 20G) formed on the second surface (VS2), first metal posts (30A to 30F) that extend between the first surface (VS1) and the second surface (VS2), second metal posts (40A to 40F) that extend between the first surface (VS1) and the second surface (VS2), and second linear conductor patterns (50A to 50F) formed on the first surface (VS1). The RFIC element (61) is disposed in the coil antenna.