Our research goal is to realize an intelligent autonomous motion for a mobile manipulator. A model task for mobile manipulators, "returning books to bookshelf" was chosen as our research task. To realize the task, we adopt a programming style named "action primitive" for programming the robot controller. Each action primitive is a basic motion control program, and the whole motion of the robot is generated by executing a sequence of action primitives step by step. The paper describes motion design for the above research task based on the action primitive concept, and reports simulation results of the designed motion.