In this paper, we assume that an output sensor of a ball and beam system is coupled with AC measurement noise. We propose an output feedback controller for a ball and beam system under measurement noise of feedback sensor. Measurement noise makes feedback signals distorted, and results in performance degradation or even system failure. Therefore, we need to design a robust controller to accommodate the possible measurement noise in the feedback information. Our controller is equipped with a gain-scaling factor to minimize the effect of measurement noise in output feedback information. We give an analysis of the controlled system and illustrate the improved control performance via simulation and experiment for a ball and beam system.