a magnetic bubble memory device according to this invention comprises a plurality of minor loops , a read - out major line is disposed at one end of the minor loops through gates having a replicating function , and a magnetic bubble detector which includes a detecting line is disposed at one end of the major line . further , a propagation length from the other end of the read - out major line to the detecting line of the magnetic bubble detector is set at a bit length which slightly exceeds four times the number of the minor loops . for this reason , a continuous read - out operation at high speed is permitted without the influence of replicate pulses .