A workpiece unit that includes a workpiece, a tape stuck to the workpiece; and an annular frame to which an outer circumferential edge of the tape is stuck and which has an opening defined centrally therein. The workpiece is disposed in the opening in the annular frame and supported on the annular frame by the tape, and at least one of the tape and the annular frame has an irreversible discoloring section that discolors in response to an external stimulus. Such a configuration makes it possible to determine whether or not a process involving an external stimulus has been carried out on the workpiece unit, based on the appearance of the workpiece unit (i.e., based on whether the irreversible discoloring section has been discolored or not).