A coupling inductor comprising: a magnetic core having a central section (C1) and an outer section (C2); a first coil (L1) wound around the central section (C1) between a first end (C12) and a center portion (C11) of the central section (C1); a second coil (L2) wound around the central section (C1) between the first coil (L1) and the center portion (C11), a third coil (L3) connected to the first coil (L1) and wound around the central section (C1) between a second end (C13) and the center portion (C11) of the central section (C1), and a fourth coil (L4) connected to the second coil (L2) and wound around the central section (C1) between the second end (C13) and the third coil (L3), wherein the first to fourth coils are all wound in a same geometrical winding direction seen from a same viewing direction, two inductors are formed by the first coil (L1) and the third coil (L3) and by the second coil (L2) and the fourth coil (L4), respectively, wherein each of the two coils of one inductor is magnetically coupled to a respective one of the coils of the other inductor, one end of the first coil (L1) facing the first end (C12) is connected to an input section (IN), another end of the first coil (L1) facing the center portion (C11) is connected to one end of the third coil (L3) facing the center portion (C11), and another end of the third coil (L3) facing the second end (C13) is connected to an output section (OUT2), and one end of the fourth coil (L4) facing the second end (C13) is connected to the input section, another end of the fourth coil (L4) facing the center portion (C11) is connected to one end of the second coil (L2) facing the center portion (C11), and another end of the second coil (L2) facing the first end (C12) is connected to another output section (OUT1). a magnetic core having a central section (C1) and an outer section (C2); a first coil (L1) wound around the central section (C1) between a first end (C12) and a center portion (C11) of the central section (C1); a second coil (L2) wound around the central section (C1) between the first coil (L1) and the center portion (C11), a third coil (L3) connected to the first coil (L1) and wound around the central section (C1) between a second end (C13) and the center portion (C11) of the central section (C1), and a fourth coil (L4) connected to the second coil (L2) and wound around the central section (C1) between the second end (C13) and the third coil (L3), wherein the first to fourth coils are all wound in a same geometrical winding direction seen from a same viewing direction, two inductors are formed by the first coil (L1) and the third coil (L3) and by the second coil (L2) and the fourth coil (L4), respectively, wherein each of the two coils of one inductor is magnetically coupled to a respective one of the coils of the other inductor, one end of the first coil (L1) facing the first end (C12) is connected to an input section (IN), another end of the first coil (L1) facing the center portion (C11) is connected to one end of the third coil (L3) facing the center portion (C11), and another end of the third coil (L3) facing the second end (C13) is connected to an output section (OUT2), and one end of the fourth coil (L4) facing the second end (C13) is connected to the input section, another end of the fourth coil (L4) facing the center portion (C11) is connected to one end of the second coil (L2) facing the center portion (C11), and another end of the second coil (L2) facing the first end (C12) is connected to another output section (OUT1). <EOS>