An image sensing device includes a pixel array including a plurality of unit pixels consecutively arranged and structured to generate an electrical signal in response to incident light by performing photoelectric conversion of the incident light. The unit pixels are isolated from each other by first device isolation structures. Each of the unit pixels includes a photoelectric conversion element structured to generate photocharges by performing photoelectric conversion of the incident light, a floating diffusion region structured to receive the photocharges, a transfer transistor structured to transfer the photocharges generated by the photoelectric conversion element to the floating diffusion region, and a well tap region structured to apply a bias voltage to a well region. The well tap region is disposed at a center portion of a corresponding unit pixel.