We developed hydraulically driven micro-forceps that can measure force when holding an object. The system uses Pascal's principle to measure small forces acting on the tips of the forceps. The holding force is calculated by determining changes in the internal pressure of the forceps. The trial-production forceps can measure very small forces, and surgeons using them can feel a force response when holding a model blood vessel. Previously developed forceps were not able to measure holding force accurately over a long period of time. The previous system used a syringe to supply water to the forceps. The syringe structure was suitable for supplying water with precision, but there was a gap between the cylinder and plunger. A leak occurred when the syringe supplied water to the forceps, causing the internal pressure acting on the forceps to decrease. The new system prevents leaking by suppling water with a bellows structure. The bellows were produced with a 3D printer that used light shaping. The structure, which was made through additive manufacturing, does not have a gap between the cyclinder and plunger, and it correctly measured internal pressure because there was no water leak. The new system can measure force with precision for an extended period of time when the forceps hold an object. This report describes the new water-supply system that was made through additive manufacturing and the results of our evaluation of its measurement precision and durability. This work was supported by JSPS KAKENHI Grant Number 15K05891.