The invention relates to medicine, or exactly to methods of non-invasive investigations of a living organism state, in particular, for diagnostics of pathological changes in tissues of human and animals organism. The apparatus relies upon illuminating the investigated organ of the body with infrared radiation of 0.6-1.5 um wavelength range and simultaneous scanning of the investigated organ volume with a focal spot of a focused beam of amplitude-modulated ultrasound waves, at least one of the parameters which appear as a result of the transmitted and/or back scattered infrared radiation being recorded. The presence and the type of pathology in the investigated organ is judged by the value and/or the characteristics of the relative changes in the above mentioned parameters during the scanning process.