We have fabricated an Fe 67.46 B 22.5 Nd 6.3 Nb 3.74 magnetic metallic glass thin film on a (100) silicon substrate by electron cyclotron resonance ion beam sputtering. We confirmed the metallic glass state of the thin film by observing its crystallographically amorphous state using X-ray diffractometry and transmission electron microscopy, and we obtained the glass transition temperature using differential scanning calorimetry. We also confirmed the magnetization of the thin film using a physical property measurement system. The thin film showed the largest reported width of the supercooled liquid region (96 K) and the smallest reported value of coercivity (7.5 A/m) among the existing magnetic metallic glass thin films. This study is expected to lead to an increase in the variety of materials available and greater knowledge of the physical properties of magnetic metallic glass thin films and to facilitate research on developing magnetic metallic glass thin films as base materials for magnetic microelectromechanical systems.