An apparatus and a program are provided which are capable of simultaneously measuring, evaluating, imaging and displaying the biological function of sites with different biological functions, such as the brain and the muscle, different parts of the brain or different muscle locations, using near-infrared spectroscopy. In an apparatus for evaluating biological function K, physiological indices, including parameters derived from changes in deoxyhemoglobin concentration and changes in oxyhemoglobin concentration, are calculated by a calculating part of a controller. To measure simultaneously, evaluate, image and display the biological functions of sites with different biological function, such as the brain and the muscle, different parts of the brain or different muscle locations, these physiological indices from different sites of the living body are adjusted in such a way that they can be compared with each other by the calculating part and displayed by a display part.
