The method of dicing a wiring substrate that includes a core substrate having a front surface and a rear surface at least one of which is provided with an adhesive layer and a rim pattern thereon. The adhesive layer is provided with a laminate that has wiring layers and insulating layers, laminating. The rim pattern is provided with the insulating layers laminated thereon. The method includes steps of forming separation grooves by removing portions of the insulating layers laminated on the rim pattern to expose the rim pattern; exposing at least one of the front and rear surfaces of the core substrate by dissolving and removing the rim pattern of the groove bottoms; and dicing the core substrate exposed at groove bottoms, along cutting margins each being smaller than a groove width of each of the groove bottoms.