A circuit board, comprising a substrate and a magnetic core, wherein the magnetic core is in an annular shape and the magnetic core has an inner side and an outer side, wherein the magnetic core is embedded into the substrate, at least one turn of a winding conductor wound around the magnetic core is arranged on the substrate, each turn of the winding conductor comprises a first end-surface conductor (41, 41') and a second end-surface conductor (42, 42') that are separately arranged on two ends of the magnetic core, and each turn of the winding conductor further comprises a first side-surface conductor (43, 43') that penetrates through the inner side of the magnetic core and a second side-surface conductor (44, 44') that is arranged on the outer side of the magnetic core, wherein the first side-surface conductor (43, 43') is electrically connected to the first end-surface conductor (41, 41') and the second end-surface conductor (42, 42'), and the second side-surface conductor (44, 44') is electrically connected to the first end-surface conductor (41, 41'), wherein: top and bottom ends of the substrate are end surfaces, wherein the end surfaces comprise a front surface and a rear surface that are oppositely arranged, and an outer peripheral wall of the substrate is a side surface of the substrate; an area formed by projection of the magnetic core on the front surface or rear surface of the substrate is an area in which the magnetic core is located; the first end-surface conductor (41,41') is arranged on the front surface of the substrate, and the second end-surface conductor (42, 42') is arranged on the rear surface of the substrate; the winding conductor has at least two turns, and the winding conductor comprises a first turn of the winding conductor and a second turn of the winding conductor, a first electronic component is arranged on the front surface of the substrate, and the magnetic core is horizontally arranged, wherein the first electronic component is located outside the area in which the magnetic core is located; the first end-surface conductor of the first turn of the winding conductor is connected to the first electronic component and extends to the area in which the magnetic core is located, the first side-surface conductor of the first turn of the winding conductor is a first conductive via hole, the first end-surface conductor of the first turn of the winding conductor is electrically conductive to a metal layer on the rear surface of the substrate through the first conductive via hole, the second end-surface conductor of the first turn of the winding conductor is connected to the first side-surface conductor of the first turn of the winding conductor, extends to the side surface of the substrate, and is connected to the second side-surface conductor, and the second side-surface conductor of the first turn of the winding conductor is arranged on the side surface of the substrate and connected to the second end-surface conductor of the second turn of the winding conductor; the first end-surface conductor of the second turn of the winding conductor is connected to the second side-surface conductor of the second turn of the winding conductor and extends to the area in which the magnetic core is located, the first side-surface conductor of the second turn of the winding conductor is a second conductive via hole, the first end-surface conductor of the second turn of the winding conductor is electrically conductive to the metal layer on the rear surface of the substrate through the second conductive via hole, the second end-surface conductor of the second turn of the winding conductor is connected to the first side-surface conductor of the second turn of the winding conductor and extends to the side surface of the substrate, and the second side-surface conductor of the second turn of the winding conductor is arranged on the side surface of the substrate and connected to the second end-surface conductor of the second turn of the winding conductor.