We have proposed a method to grasp unknown objects of arbitrary shape. In this method, the environment of an object is reproduced in a grasping simulator and approach directions for the robot manipulator to grasp the object are generated in the simulator based on a rule. Then, the manipulator is controlled along each of the generated directions in the grasping simulator to check whether the grasping from the direction is possible or not. Each feasible grasp is evaluated by a criteria function and the best grasp is selected. In this article, we tested this method with 12 unknown objects in real environment.