In an optical computing device in which a plurality of microcells provided in a matrix form are disposed so as to be stacked on each other, reduced are variations which occur in cell size and position due to dehydration and shrinkage. An optical computing device (10) includes a plurality of light diffraction layers (L1, L2, L3) stacked on each other. In the optical computing device (10), each light diffraction layer (L1, L2, L3) includes a plurality of microcells (Cijk) which have refractive indexes set individually and which are provided in a matrix form. The plurality of light diffraction layers (L1, L2, L3) are contained in a dried gel (11).