Abstract: A tape driving apparatus includes both supply and takeup reel diameter detectors so as to compute the inertia of both the reels, wherein the acceleration/deceleration torque information spent in the acceleration/deceleration of the take-up reel is detected from the take-up reel torque information so as to compute the take-up reel acceleration/deceleration compensating torque from the acceleration/deceleration torque information, both the reel diameters, and the inertia information, and the supply reel torque is controlled with the information with the computed results and the back torque information proportional to the supply reel diameter being added to it. The the access property of the tape is thereby improved.