A deformation measuring method using electronic speckle pattern interferometry comprises the steps of subtracting an average intensity from the intensity in a time domain at each point of a speckle pattern image so as to compute the cosine component of intensity; subjecting the cosine component to Hilbert transform in a temporal domain so as to compute the sine component of intensity; determining the arctangent of the ratio between thus computed sine and cosine components so as to determine an object phase; carrying out an unwrapping operation; and outputting three-dimensional deformation distribution data in a displayable mode.