Breathing crack detection and evaluation on a beam under random loading is experimentally studied and realized using entropy measures. During testing, the beam is subjected to random excitations which is the most evident excitation type experienced by most of the engineering structures. Frequency response function is employed to erase the random frequency components due to the excitation from the response of the structure to pick up the vibration characteristics of the beam structure itself with/without the breathing crack. Based on experimental results, the proposed methodology can clearly discriminate a crack with 25% depth of the total thickness of the beam from the healthy case. It is also capable of distinguishing a 50% crack depth from a 25% crack depth with distinct entropy values.