An in-chamber maintenance apparatus may include a stage module including a stage body in a chamber having a hollow interior, an XY stage mounted on an upper surface of the stage body and movable in an X-axis and a Y-axis direction perpendicular to each other, and a first driving portion configured to drive the XY stage, and a gripper module including a gripper body coupled to an upper surface of the XY stage, a gripping portion supported by the gripper body and configured to move up and down and rotate with respect to a Z-axis perpendicular to the X-axis and the Y-axis to be inserted into the hollow interior, and a second driving portion configured to drive the gripping portion.