Ni-based amorphous alloys containing no metalloids are developed in the alloy system Ni-Zr-Al-Y. A partial replacement of Zr by Y significantly enhances the glass-forming ability and enlarges the undercooled liquid region during continuous heating of amorphous ribbons. A quaternary alloy Ni55Zr17Al11Y17 exhibits large undercooled liquid region (54 K) implying high glass-forming ability of the alloy. The glass transition and crystallization temperatures of the quaternary alloy obtained in a differential scanning calorimetry are 717 and 771 K, respectively. A fully amorphous rod (Φ1 mm) and a rod (Φ2 mm) having a high volume fraction (∼80%) of the amorphous phase can be prepared by copper mold injection casting.