A processing apparatus and a processing method with which an object-to-be-cut is processed, and a high-precision superconducting acceleration cavity can be formed. The processing apparatus forming a half cell by processing a hollow workpiece, and is provided with a securing jig, a rotational drive portion rotating the securing jig, and a cutting tool. The securing jig having a plurality of members, when cutting a first portion-to-be-cut of the workpiece, the plurality of members are combined in a first pattern so that the first portion-to-be-cut is exposed, when cutting a second portion-to-be-cut of the workpiece, the plurality of members are combined in a second pattern so that the second portion-to-be-cut is exposed, and the combination of the plurality of members is changed from the first pattern to the second pattern without removing the workpiece.