Few interface systems designed to control continuum robots have been developed. This work presents a master device for multi-unit continuum robots. The master mechanism has the same kinematic structure as the slave device. The kinematic structure, which uses a spring as a backbone, allows for a unique forward kinematic solution. This design is slim-sized, light-weight, and easy to implement. As an example mechanism, a continuum unit with two degrees of freedom was developed. Two-unit modules were assembled to generate four degrees of freedom. The performance of the master device is verified through a master-slave control experiment.