To provide polishing device and polishing method for especially polishing semi-sphere recessed surface and semi-sphere projecting surface, etc., with high accuracy with a long service life of an injection tool and excellent machining stability, and optical element and exposing device polished by the polishing method.

In this polishing device 8, an injection part 1a is provided at a distal end of the injection tool 1 and surface polishing of a polishing object 2 is performed by injecting gas 4 from the injection part 1a by interposing polishing liquid 3 between the injection part 1a and the polishing object 2. The injection part 1a has a hollow spherical shape and has a plurality of injection ports 1b to inject the gas 4.