According to an embodiment, a magnetic storage device includes a semiconductor region including a trench; a gate electrode disposed in the trench; an insulation film covering the gate electrode and provided in a manner to fill the trench; and a magnetoresistive effect element including at least a first ferromagnetic layer, a second ferromagnetic layer, and a non-magnetic layer provided between the first ferromagnetic layer and the second ferromagnetic layer, the non-magnetic layer in a side surface of the magnetoresistive effect element including the non-magnetic layer being provided on a top surface of the insulation film.