There are provided a storage device and a storage unit capable of improving retention performance of an intermediate resistance value in writing at a low current, and a storage device and a storage unit capable of reducing random telegraph noise. A storage device of one embodiment of the present technology includes a first electrode, a storage layer, and a second electrode in this order, and the storage layer includes: an ion source layer including one or more kinds of chalcogen elements selected from tellurium (Te), sulfur (S), and selenium (Se), and one or more kinds of transition metal elements selected from Group 4 elements, Group 5 elements, and Group 6 elements of the periodic table; and a resistance change layer including boron (B) and oxygen (O). A storage device of another embodiment of the present technology includes the above-described ion source layer and a resistance change layer including one or more kinds of transaction metal elements selected from Group 4 elements, Group 5 elements, and Group 6 elements of the periodic table, and oxygen (O).