A magnetic component and a transformer are provided by the present disclosure. The magnetic component includes: at least three core columns; and a winding wound around at least one of the at least three core columns; wherein a medium having a relative initial permeability equal to 1 is disposed on at least one side of the at least three core columns. In the present disclosure, a conventional magnetic cover board with a high relative initial permeability is replaced by a medium with a relative initial permeability (ur) satisfied ur=1, such as air or a cover board.