A slave device attachable to an end effector and configured to perform an end effector replacement by which an end effector before replacement is removed from the slave device and an end effector after replacement is mounted on the slave device, the slave device comprising: a communication part, configured to communicate with the end effector after replacement mounted on the slave device after the end effector replacement; a storage part, configured to store, with regard to each of a plurality of attachable end effectors that are attachable to the slave device, communication information of a communication form between the slave device and the attachable end effector; and a communication setting change part, configured to automatically change a communication setting in the communication part according to the communication information which corresponds to the end effector after replacement in a time required for a movement of the slave device during the end effector replacement when the end effector after replacement is one of the plurality of attachable end effectors, wherein the slave device is characterized by further comprising a priority control part configured to control priority of tasks of a software in the communication setting change part, which tasks are configured to perform the change of communication setting, and to calculate a track of the movement of the slave device to obtain a time required for the movement of the slave device, the priority control part being further configured to raise the priority of the tasks in the communication setting change part when a time for the communication setting change part to change the communication setting in the communication part is longer than the obtained time required for the movement of the slave device conducted in the end effector replacement, wherein the movement of the slave device is to locate an attachment part for the end effector in the slave device conducted in the end effector after replacement, wherein the time for the communication setting change part to change the communication setting is a sum of a software treatment time and a hardware access time in the communication part, and wherein a difference between the communication form of the end effector before replacement and the communication form of the end effector after replacement includes a difference in communication medium, a difference in communication mode, and a difference in protocol. a communication part, configured to communicate with the end effector after replacement mounted on the slave device after the end effector replacement; a storage part, configured to store, with regard to each of a plurality of attachable end effectors that are attachable to the slave device, communication information of a communication form between the slave device and the attachable end effector; and a communication setting change part, configured to automatically change a communication setting in the communication part according to the communication information which corresponds to the end effector after replacement in a time required for a movement of the slave device during the end effector replacement when the end effector after replacement is one of the plurality of attachable end effectors, wherein the slave device is characterized by further comprising a priority control part configured to control priority of tasks of a software in the communication setting change part, which tasks are configured to perform the change of communication setting, and to calculate a track of the movement of the slave device to obtain a time required for the movement of the slave device, the priority control part being further configured to raise the priority of the tasks in the communication setting change part when a time for the communication setting change part to change the communication setting in the communication part is longer than the obtained time required for the movement of the slave device conducted in the end effector replacement, wherein the movement of the slave device is to locate an attachment part for the end effector in the slave device conducted in the end effector after replacement, wherein the time for the communication setting change part to change the communication setting is a sum of a software treatment time and a hardware access time in the communication part, and wherein a difference between the communication form of the end effector before replacement and the communication form of the end effector after replacement includes a difference in communication medium, a difference in communication mode, and a difference in protocol.