A stacking die comprises a stacked multiple stacking plates and a side plate(s) which fixes the multiple stacking plates in a stacked state, wherein at least one or more processing object(s) is retained in a space(s) formed between the multiple stacking plates. Further, surfaces where the stacking plates and the side plate(s) abut each other are preferably tapered so that they form tapered shapes in a direction opposite to the approach direction of the side plate(s).