This paper describes a prototype of car sharing system using a self-driving car. We use 3D range sensor for detect road boundaries. First, we detect curb positions and fit a line to them with RANSAC. Based on the fitting result, we classify the boundary into straight or circular, and estimate the parameter for each class. These parameters are used for controlling the car to follow the road or turn a comer. We also develop a browser-based car-calling system by which a user can call the car using map and GPS data. The car sets the user location from the specified GPS data and moves there autonomously. When the car arrived, the user switches the car to the manual-driving mode and starts driving. When arrived at the destination, he/she switches the car to the self-driving mode and just gets off. The develop system shows the feasibility of a new type of car sharing system.