A data processing apparatus comprising: memory means for storing a data set including a plurality of data elements (E1,..., Ei) and a first Bloom filter used in a membership test process to determine whether a query-target data element is present in the data set and having specific bits set to a specific value, the specific bits being determined by predetermined calculation using the plurality of data elements, respectively; and calculating means for: deleting, when some data elements (E11, E12, E13) are deleted from the data set, a first bit array from an end of a bit array of the first Bloom filter, the first bit array having a number of bits corresponding to a number of the some data elements; and running a membership test when a first data element is entered as a query-target data element after deleting the first bit array, the running including: adding a second bit array temporarily at an end of a bit array of a second Bloom filter, the second Bloom filter being obtained by the deleting of the first bit array from the first Bloom filter, the second bit array having a same number of bits as the first bit array, with all bits set to the specific value; and determining, using the second Bloom filter with the second bit array added thereto, whether the first data element is present in the data set from which the some data elements have been deleted. memory means for storing a data set including a plurality of data elements (E1,..., Ei) and a first Bloom filter used in a membership test process to determine whether a query-target data element is present in the data set and having specific bits set to a specific value, the specific bits being determined by predetermined calculation using the plurality of data elements, respectively; and calculating means for: deleting, when some data elements (E11, E12, E13) are deleted from the data set, a first bit array from an end of a bit array of the first Bloom filter, the first bit array having a number of bits corresponding to a number of the some data elements; and running a membership test when a first data element is entered as a query-target data element after deleting the first bit array, the running including: adding a second bit array temporarily at an end of a bit array of a second Bloom filter, the second Bloom filter being obtained by the deleting of the first bit array from the first Bloom filter, the second bit array having a same number of bits as the first bit array, with all bits set to the specific value; and determining, using the second Bloom filter with the second bit array added thereto, whether the first data element is present in the data set from which the some data elements have been deleted. deleting, when some data elements (E11, E12, E13) are deleted from the data set, a first bit array from an end of a bit array of the first Bloom filter, the first bit array having a number of bits corresponding to a number of the some data elements; and running a membership test when a first data element is entered as a query-target data element after deleting the first bit array, the running including: adding a second bit array temporarily at an end of a bit array of a second Bloom filter, the second Bloom filter being obtained by the deleting of the first bit array from the first Bloom filter, the second bit array having a same number of bits as the first bit array, with all bits set to the specific value; and determining, using the second Bloom filter with the second bit array added thereto, whether the first data element is present in the data set from which the some data elements have been deleted. adding a second bit array temporarily at an end of a bit array of a second Bloom filter, the second Bloom filter being obtained by the deleting of the first bit array from the first Bloom filter, the second bit array having a same number of bits as the first bit array, with all bits set to the specific value; and determining, using the second Bloom filter with the second bit array added thereto, whether the first data element is present in the data set from which the some data elements have been deleted.