A magnetic component and a switch power supply device are disclosed. The magnetic component includes a magnetic core and at least three windings, the magnetic core including at least three winding columns, at least one side columns, a first cover plate and a second cover plate opposite to each other, wherein the at least three winding columns are sequentially arranged in adjacent, the first cover plate and the second cover plate are respectively at upper parts or lower parts of the at least three winding columns and the at least one side column to form a closed magnetic flux loop; the at least three windings are wound on the at least three winding columns, respectively; wherein magnetic flux direction of the middle winding column in adjacent three winding columns is opposite to magnetic fluxes direction of the other two winding columns in adjacent three winding columns.