This paper describes the development of one DoF robotic hand that makes human laugh by tickling through rubbing underarm. Laughter is attracting research attention because it enhances health by treating or preventing mental diseases. However, laughter has not been used effectively in healthcare because the mechanism of laughter is complicated and is yet to be fully understood. The development of a robot capable of making humans laugh is useful for clarifying the mechanism of laughter because the stimuli by the robot is quantitative and reproductive. Especially, tickling matches to this purpose because the relationship between stimuli and reaction is simpler compared to other techniques. Therefore, this research aimed to develop a robotic hand that can output quantitative and reproductive tickling stimuli for clarifying the mechanism of laughter. Rubbing underarm is selected as a target motion of robot because previous research suggested that this is the best way for making humans feel ticklish. In order to achieve the tickling motion by robots as humans, the required specifications were determined through experimental method. In order to develop a robot that achieves the required fingertip trajectory by simple mechanisms as much as possible, mechanism with crank and link driven by single motor was developed. The result of experimental evaluation shows that the developed robot could make humans laugh by its rubbing motion. In addition, the quantitative tickling motion by developed robotic hand was suggested to be effective for clarifying the mechanism of laughter.