Wall painting is a repetitive, exhausting and dangerous process that makes it an ideal case for automation. Paint had been automated in the automotive industry but not yet for the construction industry. There is a great need for a mobile robot that can be moved to paint the interior walls of residential buildings. This article describes the conceptual design of an autonomous mural painting robot consisting of an arm that scans the walls vertically and is mounted on a mobile robot base to give the lateral feeding movement to cover the painting area. The aim of the design is to meet the criteria of simplicity, low weight, low cost and fast paint time. Ultrasonic sensors are installed on the arm and mobile base to adjust the limits of movement and maneuver in the room area. A control system is designed to guide the movement of the arm and to plan the movement of the moving base.