1. A biological-information obtaining apparatus comprising: light-emitting means for emitting light; image-capturing means for capturing images, in time sequence, obtained by irradiating a living body with the light emitted and by causing the light to be transmitted through or reflected by the living body, the image-capturing means being sensitive to at least two color components; extreme generation means for generating a maximum value and a minimum value, in time sequence, of each of the color components for certain regions of the captured images; and oxygen-saturation calculation means for calculating oxygen saturation on the basis of the maximum value and the minimum value of each of the color components.