1. A robot including a controller which controls the robot to execute a task by making autonomous motions according to communication with a support server provided with a task database, the controller comprising: a first processing element configured to: communicate with the support server and recognize a content of a designated task among a plurality of tasks stored in the task database; evaluate a cost indicating a labor or load required for the robot to execute the designated task; communicate with the support server and store the evaluated cost for the robot to execute the designated task in the task database; evaluate the cost of a scheduled execution task for the robot when the designated task has been executed and evaluate the cost of the scheduled execution task for the robot when the designated task is not executed after an execution duration of the designated task, respectively; evaluate the cost for the robot to execute the designated task to continuously or step-wisely increase as the cost of the scheduled execution task when the designated task has been executed becomes higher as compared to the cost of the scheduled execution task when the designated task is not executed; and evaluate the cost for the robot to execute the designated task to continuously or step-wisely decrease as the cost of the scheduled execution task when the designated task has been executed becomes lower as compared to the cost of the scheduled execution task when the designated task is not executed; and a second processing element configured to recognize whether the cost for the robot to execute the designated task stored in the task database is a lowest cost for execution of the designated task in a robot group containing other robots, and to control the motions of the robot to execute the designated task on a condition that the cost thereof has been recognized to be the lowest.