A signal arrival direction deducing device capable of deducing the signal arrival direction even when a correlation matrix between input signals and noise correlation matrix are singular. A state is observed in which only noise is present and a state is observed in which a sound whose arrival direction is to be deduced. A short time Fourier transform is performed. Correlation matrix and an input signal correlation matrix are used to compute proper eigenvalues/proper eigenvectors and improper eigenvectors of the noise correlation matrix with respect to the input signal correlation matrix. A matrix for determining the complementary space component of the signal partial space is computed from the proper eigenvectors and the improper eigenvectors. An arrival direction search is made for the sound arrival direction using the matrix for determining the complementary space component of the signal partial space.