Changes of intensity distributions of the laser speckle pattern reflected from the aluminum surface under plastic deformation were measured using the image processing technique. The cross section of the laser speckle pattern on a same gray level changed to the ellipsoidal shape from the initial circular shape corresponding to the onset of plastic anisotropy of aluminum. Therefore, the cross section of the speckle pattern was approximated by an elliptic function using the least squares method. The results obtained are as follows. (1) Changes of radii a and b and aspect ratio b/a of the elliptic function approximating the cross section of the laser speckle pattern under plastic deformation are related to the onset of plastic anisotropy, the onset of yielding and localized deformation. (2) In the case of the rolled specimen, changes of the aspect ratio can be divided into the three stages : first is the negligible change in the elastic deformation, second is the large change until the onset of localized deformation and third is the small change after that. (3) In the case of the annealed specimen, the changes of radii a and b due to plastic deformation were very large, but the change of the aspect ratio was very small.