This paper proposes a new task selection method for multi-task communication robots. As robot technology improves, communication robots are being used in public places. These communication robots are meant to perform patrol, promotion, or guidance activities in place of humans. When a communication robot is implemented for multiple purposes, it is important that the robot be able to appropriately select its own tasks. In this paper, we propose a collaborative task casting method to support communication robots when they are selecting a task. We also describe the implementation of a task management system based on the proposing method. This system takes into account global task achievement and balances task occupation to ensure that adequate robot resources are directed towards each task.