PURPOSE: To provide a magnetic recording/reproducing device capable of calculating a tape residual time from a present position to a tape end at the precision same as at the time of low speed running even when a tape runs at a high speed, the time required for one revolution of a tape feeding part and a tape take-up part becomes remarkably short and no measurement error of a time measuring part is ignored.

CONSTITUTION: This device is provided with a tape driving part 11 for driving the tape, a drive control signal detection part 12 detecting a drive control signal generated by the tape driving part, a tape running control part 13 deciding driving force for stably running the tape and a remaining tape calculation part 17 calculating the tape residual time by information sent from the drive control signal detection part 12. Thus, a remaining tape calculating function capable of calculating the tape residual time at the precision same as at the time of low speed running is obtained even when the tape runs at a high speed.