A data transfer device includes: a plurality of masters each having a buffer and configured to calculate a remaining-time counter based on an amount of data in the buffer; a memory system configured to perform data transfer with the plurality of masters and having a memory access prohibition period during which access from the plurality of masters is intermittently prohibited; a bus arbiter configured to arbitrate the plurality of masters based on the remaining-time counter; and a remaining-time counter-adjusting part configured to add a remaining-time counter offset, which adjusts the remaining-time counter until the start of the memory access prohibition period, to at least one of the plurality of masters.