A magnetic head of an embodiment includes a stack, side shields, and a first and a second magnetic shield. The stack includes a pin layer having a fixed magnetization direction, a first free layer having a magnetization direction to change in accordance with an external magnetic field, a second free layer antiferromagnetically exchange-coupled with the first free layer and having a magnetization direction to change in accordance with the field, and an antiferromagnetic layer exchange-coupled with the second free layer. A magnetic field is applied from the side shields to the first and second free layers, and a direction of the magnetic field is substantially parallel to the magnetization direction of one of the first and second free layers and substantially antiparallel to the magnetization direction of the other, and a magnetic volume of the one is larger than a magnetic volume of the other.