A regeneration apparatus for an electroless plating solution, which includes a sensor for measuring the formation rate of phosphorous acid formed in a plating tank in response to a plating treatment, a split device for taking out a plating solution in the plating tank to transfer the plating solution to a first processing tank, a sensor for measuring the concentration of the phosphorous acid contained in the plating solution taken out, an addition device for supplying calcium carbonate or calcium hydroxide, an amount of which is required for producing a calcium phosphite from the phosphorous acid contained in the plating solution, to the first processing tank, a separation device for separating and removing the calcium phosphite produced in the first processing tank from the plating solution, and a return pump for transferring the plating solution from which the calcium phosphite has been separated and removed to the plating tank.