A sensing device for sensing ion concentration of a solution, including a first substrate, a second substrate, a sensing layer, and two electrodes. The material of the first substrate includes cellulose. The second substrate is located on the first substrate. The sensing layer is located on the second substrate. The two electrodes are separately disposed on the sensing layer to expose the sensing layer and bring a solution in contact with the sensing layer so as to measure the resistance value of the solution and convert the resistance value into the ion concentration of the solution.
