To optimize a processing for reading a search object data from a storage device, to improve a processing speed of two division search and to shorten whole processing time required for two division search through the use of a single port memory whose read-out speed is the same as a former one.

Two division search is executed in order from the left of tree of search addresses. The search addresses are arranged so that a search address whose LSB (lowest bit) is zero is an even address and that whose LSB is '1' is an odd address and the two addresses being next search objects can simultaneously be read in the tree. Search object data are separated into data of an even address and those of an odd address in the successive addresses and they are allocated to the two storage devices. Then, reading of the two storage devices is performed simultaneously and the reading/comparison of data can be processed in parallel.