Definitely ancient; this type was made from about 348-358, over a century before the fall of Rome in 476. Most use the fall of Rome as the cutoff between ancient and medieval, although from a numismatic standpoint, I consider "medieval" to start in about 550-600, after Justinian, and after the Gothic kingdoms had been driven out by kingdoms formed from former Roman subjects.
Ancients really aren't all that bad; you can collect just about the entire Constantinian dynasty in XF/AU for under $150!