A deduplicate device includes: a first through N-th (N≧3) bloom filters; a counting unit that performs a process of judging whether information indicating that a duplicate data of a storing-target data exists in a storage device is registered in each bloom filter sequentially until an unregistered bloom filter in which the information is not registered is found or that the information is registered in the N-th bloom filter is found, and registers, when the unregistered bloom filter is found, the information indicating that the duplicate data exists into the unregistered bloom filter; and a deduplicating unit that stores the storing-target data in the storage device when the counting unit finds the unregistered bloom filter, and stores index information relating the duplicate data in the storage device with the storing-target data when the counting unit finds that the information is registered in the N-th bloom filter.