The winding (36) of a choke coil (31) is densely wound in a single layer around the outer periphery of tubular barrel (33) of a bobbin (32), and a winding (37) is densely wound in a single layer overthe winding (36). A winding (46) is densely wound in a single layer around the outer periphery of tubular barrel (43) of a bobbin (42), and a winding (47) is densely wound in a single layer over the winding (46). Windings (36), (37), (46), (47) are wound so as to mutually intensify magnetic fluxes when an in-phase noise current flows. Windings (36, 37) carry out a differential transmission communication and are connected with a pair of signal lines working as the go path of a power supply current. Windings (46, 47) carry out a differential transmission communication and are connected with a pair of signal lines working as the return path of a power supply current. Accordingly, a circuit using a choke coil small in size, large in inductance, and excellent in high-frequency characteristics,and the choke coil are provided.