Answer:
No. A cantilever bridge is not a beam bridge. A beam bridge and a cantilever bridge are two separate types of bridges.
However, a cantilever bridge could be said to be a variation on the basic beam bridge. The roadway of the bridge is held in place by cantilevers, which are long structures, or arms, projecting out into the water, but which are anchored on only one end. A diving board is a good example of a cantilever: although anchored on only one end, it can support a lot of weight.
In a cantilever bridge, there are the outer beams, the cantilevers, and the central beam. The outer beams are attached firmly to shore, while the cantilevers are then attached to these outer beams. The cantilevers projecting out from the outer beams, or supporting piers on the opposite shores, are then joined by a central beam.