The present invention provides an inorganic oxide made of MLn2QR4O12, where M is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba; Ln is at least one rare earth element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; Q is at least one element selected from the group consisting of Si, Ge, Sn, and Pb,; and R is at least one element selected from the group consisting of B, Al, Ga, In, and Tl. This inorganic oxide serves as a phosphor or a phosphor host and if it contains ions capable of being the luminescent center, it becomes a phosphor emitting fluorescent light. Thus, a novel oxide that can be a phosphor host of a high efficiency phosphor or the phosphor itself and a novel phosphor are provided.