PURPOSE: A tension display device of both bearing reels is provided to display the tension at an excellent level when calculating the relation between the length of a fishing gut and a spool. CONSTITUTION: A tension display device of both bearing reels includes a tension display unit(6)； a torque detection unit detecting the torque acting on a spool； a rotation number detection unit detecting the number of rotations of the spool； a memory unit(67) in which the relation between the reference length of a reference fishing gut and the number of rotations are stored in advance； a relation storage(74) storing the relation of the spool with the number of rotations in the memory unit； a memory reader(75) which successively reads the reference length of the fishing gut according to the number of rotations detected by the rotation number detection unit from the memory unit； a wound-gut diameter output unit(76) successively producing the diameter of a wound gut； and a tension output unit(77) producing the tension based on the torque detected by the torque detection unit and the calculated wound gut diameter. [Reference numerals] (5) Adjusting lever； (60) Reel control unit； (61) Display unit； (62) Operation key unit； (63) Spool sensor； (64) Spool counter； (65) Buzzer； (66) Motor driving circuit； (66a) Current detecting unit； (67) Memory unit； (70) Motor control unit； (71) Display control unit； (72) Water depth display unit； (73) Tension display unit； (74) Relation storage； (75) Memory reader； (76) Line winding diameter calculating unit； (77) Tension calculating unit； (78) Correcting unit； (79) Line type setting unit； (80) Tension information change unit； (AA) Other input/output unit
