PURPOSE: To shorten retrieving time and to reduce the capacity of a semiconductor RAM and keyword comparing time by using a key code obtained by hashing a keyword.

CONSTITUTION: In the retrieving operation by a bubble memory device at the retrieval of its contents, a retrieval keyword 361 is contracted and encoded by an error correcting circuit 360 at first. The obtained key code 362 is successively compared with the contents of a rapid key code memory 350 by a key code comparator 364. Subsequently, a data block having an error correcting code coincident to the retrieval key code 362 is read out from a bubble memory device 300 through a timing control part 320 and whether the keyword in the data block coincides with the retrieval keyword 361 or not is checked by using a keyword comparator 390. As the result of the retrieving operation, the data block having the keyword coincident to the retrieval keyword is entered to a buffer memory 370.