Disclosed are a plasma generator and a workpiece processing apparatus, wherein an adapter 38 is attached to a distal end of each of a plurality of plasma generation nozzles 31 to convert a spot-shaped spout port of the plasma generation nozzle 31 to a lengthwise sport port 387, and a cover member 93 is provided to cover the plasma generation nozzles 31 so as to allow a narrow space to be defined between the cover member 93 and a workpiece, whereby plasma spouted from the spout port 387 is retained in the space in such a manner as to hit against and rebound from the workpiece into the space. This makes it possible to subject a workpiece having a relatively large surface area to plasma exposure in a uniform manner, while suppressing cooling of plasma in the space to allow the plasma to survive for a relatively long period of time (reduce a plasma disappearance rate) so as to provide enhanced efficiency of plasma exposure.