The most common of stroke is hemiplegia and it is known that finger paralysis in particular tends to remain. These patients feel inconvenient in daily life because the grasping operation becomes difficult. On the other hand, not moving the paralyzed fingers for a long term will cause joint contracture. To solve these problems, we propose applying a wearable assistive system that provides grasp-assistance for finger paralysis patients. The purpose of this research is to develop the "Exo-Finger" for grasp-assistance. The Exo-Finger is an exoskeleton system that assists the cylindrical grip that often appears during daily life. A wire is connected on the end point of the frame. When the motor pulls it, it is possible to extend the MP (Metacarpophalangeal), PIP (Proximal interphalangeal), and DIP (Distal interphalangeal) joints together. Elastics are used to assist flexion of the fingers. Moreover, we developed two kinds of control interfaces based on the state of the paralyzed finger. One is using a push switch operated by the finger as a trigger. Through the experiment with a hand mock-up, grasping operation could be achieved as grasp-assistance with Exo-Finger. In conclusion, we developed the Exo-Finger and confirmed that the Exo-Finger would be used for grasp-assistance in daily life.