To provide a reciprocating rotation number-controlling device with a simple structure capable of controlling rotations in reciprocation to the same numbers by making use of the characteristics of a constant-torque spiral spring.

A main pulley and a sub pulley are rotatably pivoted to a main shaft which is connected to a motor so as to be driven to rotate in only one direction and an independent sub shaft, respectively, and both ends of the constant-torque spiral spring are interlocked to the main and sub pulleys so as to be mutually driven and reversely wound to each other. The reciprocating number is set by constituting such that the spring is rewound to the end of its interlocking point. Further, a subsidiary main pulley is integrally pivoted by the main shaft, and a subsidiary sub pulley freely rotatable integrally with the main pulley is pivoted by the sub shaft. Both ends of a resilient spiral spring are interlocked to the subsidiary main and sub pulleys while winding in the same direction as each other to accumulate a mechanical energy to the resilient spiral spring by motor driving. Thereby, the rotation drive of the motor to the subsidiary main pulley is released at one point of unwinding finished end by the constant torque spiral spring and is started at the other point.