A magnetic device includes a housing, a bobbin, a coil, and a magnetic core. The housing has a side plate and a bottom plate. The side plate stands on the bottom plate and forms a space with the bottom plate. The bobbin is at least partially located in the space. The bobbin has a cylinder. The coil is wound around the cylinder. The coil has a portion facing the bottom plate. The magnetic core includes a center column, a side column, and a connecting portion. The center column is located in the cylinder. The side column is located outside the coil and away from the bottom plate, such that the coil is located between the side column and the bottom plate. The connecting portion connects the center column and the side column.