PURPOSE: To make a recording or a reproducing device thin by simplifying the constitution of a tape driving mechanism.

CONSTITUTION: A feeding side reel base 1 is provided with a feeding reel gear 4 having a limiter torque means which limits the driving force from a motor with the sliding movement of a felt 12 and a feeding reel disk 2 which receives the brake by a tension belt 7. Further, a take-up side reel base 8 is provided with a take-up reel gear 11 having a limiter torque means which limits the driving force from the motor with the sliding movement of the felt 12 and a take-up reel disk 9 which takes in the driving force from the motor without limiting the force. Then, a swing gear 14 engaged with a driving gear being driven by the motor is constituted to be movable to the direction of the feeding side reel base 1, to the direction of the take-up side reel base 8 and further to upward and downward directions as well by being supported by a swing arm 14 at its shaft. At the time of the rapid traverse of a magnetic tape, the take-up reel disk 9 is driven by the swing gear 14 and at the time of the rewinding of the tape, the feeding reel gear 4 is driven by the swing gear 14.