An image sensing device is disclosed. The image sensing device includes a pixel array including a plurality of unit pixels, each of which is configured to generate a pixel signal in response to incident light. The pixel array includes a substrate layer including a plurality of photoelectric conversion elements configured to convert the incident light into an electric signal, a plurality of microlenses formed over the substrate layer to respectively correspond to the photoelectric conversion elements, and configured to converge the incident light into the corresponding photoelectric conversion elements, a plurality of color filters disposed between the plurality of photoelectric conversion elements and the plurality of microlenses and configured to transmit light at predetermined wavelengths to corresponding photoelectric conversion elements, and one or more grid structures disposed over the substrate layer at intervals to separate the microlenses and the color filters from adjacent microlenses and the color filter. The grid structures have different heights at different locations in the pixel array such that one or more of the grid structure include a top portion protruding from a top surface of an abutting microlens.