Robot safety is very important when human worker and robots are working side by side in the shard space. In the early stage, force control and collision detection of the robot were performed by attaching a six-axis force/torque sensor to the robot end. However, this method was costly due to the expensive sensor and could not detect a collision occurring in the robot body. An alternative is to use a joint module equipped with a joint torque sensor (JTS) that can measure the exact torque transmitted to the link. However, the current JTS is affected by the vibration of the harmonic drive, so there is a limitation in accurate torque measurement. Furthermore, there is a problem that the stiffness of JTS is low enough to degrade the performance of the robot. The proposed joint module minimizes the error due to the torque ripple by adopting the reactive type JTS for which the location of JTS is separated from the harmonic drive and by having a ring structure which results in high stiffness and compact structure. Various experiments verified that the proposed joint module and JTS show very good performance.