This research developed novel stiffness sensing system attachable to endoscope. The system is an extension of our previous force sensing systems utilizing force visualization mechanism. The sensing part is attached to endoscopes. The force is visualized at the sensing part, and can be measured as visual information via endoscopes. The sensing part also has a structure of limiting the pressing amount. By measuring force at the limitation, the stiffness can be measured. The developed sensing part has the features of no electrical components, disposable, simple, easy sterilization, MRI-compatibility, and low-cost. The validation of the system was experimentally shown.