To inhibit an increase in the number of encoder types. A servo system (S) is provided with: a motor (M) configured such that a movable element moves relative to a stator; an encoder (100) configured so as to detect a position of the movable element; and a control device (CT) configured so as to control operation of the motor (M) on the basis of a detection result of the encoder (100). The control device (CT) is provided with a first command transmission unit (210A) configured so as to transmit, to the encoder (100), at a first speed, a change command for changing an encoder-side communication speed to a second speed which is faster than the current first speed. The encoder (100) is provided with a speed setting unit (111) configured so as to change the encoder-side communication speed to the second speed in cases when the change command has been received.