1. A direction estimation method for coherent signals in an environment of spatially correlated additive noise, where a specified number (=p<M/2) of coherent signals are received by a uniform linear array with multiple (=M) antenna elements, and the length of the spatial correlation of the noise is assumed to be q (0≦q≦M−1), comprising step of: calculating (M−q−1) instantaneous cross-correlations at time n between a signal received at an antenna element and signal s received at the other (M−q−1) antenna elements; selecting multiple pairs of the cross-correlations, each of which is consisted of p instantaneous cross-correlations from the calculated (M−q−1) instantaneous correlations to form a Hankel correlation matrix. and dividing this matrix into an upper and lower correlation matrices; calculating a linear operator at time n from these two upper and lower correlation matrices by using an adaptive LMS algorithm with a fixed or time-varying step-size parameter; estimating a noise subspace by using this estimated linear operator; and estimating the directions of the coherent signals at time n from the estimated u noise subspace by using Newton approximation.