A data transfer control device and controlling method in which data on a storage medium is read continuously. The data transfer control device includes M storage units each for storing respectively at least two kinds of different data among N kinds of data in memory regions, a transmission control element for transmitting the N kinds of data and a spare storage unit for storing at least one kind of data among said N kinds of data. The transfer control device includes a judging element for judging whether accessing any one of the M storage units must be halted. Switching element for switching a memory region to the spare storage unit and the remaining (M-1) storage unit when the judging element judges that accessing must be halted and then the switching element performs an accessing operation. The data transfer control device can suppress an increase in the device forming cost, power consumption, and installation area, and can increase the amount of data which can be stored according to the number of storage units installed.