Crack Location and depth are very important consideration in the vibration analysis of beam. The crack present in the beam or structure changes the physical nature of beam and dynamic response. In the present study vibration analysis of cantilever beam using aluminium material with and without crack. Here Ansys is used to finding the natural frequencys and amplitude of beam with and without crack and compare this result for different boundary condition. The natural frequencies of free vibration of the beam with multiple cracks are computed. It is observed that with increase in number of cracks, the natural frequency decreases. The effect of cracks is more pronounced when the cracks are near to the fixed end than free end.