PURPOSE:To detect accurately tape residual time of various tapes having differet tape thickness respectively by operating the tape thickness of a tape in operation and operating the tape residual time by using the data of tape thickness. CONSTITUTION:An angular velocity omega1 extracted from a counter 2 is stored in a memory 13 and applied to an operator 6. A tape running speed (v) from a setting device 11, a prescribed time t3 elapsed from the start time from an accumulating time generator 12, and angular velocities omega1, omega3 at start and a point of time elapsed from a prescribed by the counter 2 from the memory 13 are applied to the operating device 6, a tape thickness (d) is calculated and applied to an operator 10. The tape running speed (v) from the setting device 11, a hub diameter (r) from a hub diameter operator 7, and the angular velocity of the supply reel at start from the memory 13 are applied to the operator 10 and a tape residual amount time (t) is calculated. The time (t) is applied to a drive circuit 14 for display, where a display device drive signal corresponding to the time is obtained and applied to a tape residual amount time display device 15 for the purpose of time display.