A coil antenna is disclosed comprising a magnetic core and a wire wound around the magnetic core. The magnetic core is made of a mixture comprising soft magnetic powder and an organic binder agent. The magnetic core has a specific complex permeability whose real part is 20 or more over a frequency range of 10 MHz or less and whose imaginary part " is 10 or more over a frequency range of 10 MHz or more so that the magnetic core is also servable as a noise suppressor against high-frequency noise.