A data processing apparatus and a data amount reducing method are disclosed. The data processing apparatus includes a receiving unit and a numerical transforming unit. The receiving unit is used to receive M original detection data, wherein M is a positive integer. The numerical transforming unit is coupled to the receiving unit and used to perform a numerical transforming process on the M original detection data to generate K numerical transformed data, wherein K is a positive integer smaller than M. Therefore, the amount of the K numerical transformed data can be smaller than the amount of the M original detection data to achieve the effect of reducing the amount of data.
