The bioinstrumentation apparatus includes a light irradiation unit irradiating a measurement region with light, a light detection unit detecting diffused light from the measurement region, and a computing unit generating a reconstructed image for the interior of the measurement region. The computing unit calculates J coefficients wj set for every pixel of the reconstructed image and more than 0 and not more than 1 (where J is the number of pixels of the reconstructed image) and carries out successive approximation computation by the following iterative formulaxj(k+1)=xj(k)+wjdj(k) (where k is an integer from 1 to N, N is the number of times of iterative computation, xj(k) is a pixel value of the jth pixel on the kth iterative computation, and dj(k) is an update amount of the jth pixel on the kth iterative computation) to generate the reconstructed image.
