To provide a marine acoustic tomographic data analyzer that never has such abnormality as the reduction of the distribution of estimation error in the horizontal direction at the edge of a region.
This analyzer has the following parts. A pseudo covariance generator 1 divides the object section for function expansion into a specified number of sections and forms the sound speed variation covariance matrix, wherein the horizontal expansion function is the rectangular function, with the above described divided section as the object from marine observation data. An orthogonal Gauss-function generator 2 generates the Gauss function with the object section for function expansion as the object, displays the function as the matrix, computes the eigen vector from the matrix and forms the expansion function matrix. A linear converter 3 and a matrix aligning device 4 form the sound-speed-variation covariance matrix, wherein the orthogonal Gauss function is the horizontal expansion function, from the sound speed variation covariance matrix formed in the pseudo covariance generator 1 and the expansion function matrix formed in the orthogonal Gauss function generator 2.