To provide a porous diamond cutter for cutting pig-iron of casting or steel which has stable cuttability and durability as a new tool which is excellent in heat radiation of cutting heat and cutting quality.

This diamond cutter has a cutting edge layer which is thicker than thickness of a disc substrate 1 at the outer peripheral edge of the substrate 1. The cutting edge layer is constituted of a cutting edge part 5 having hard abrasive grain 4 by being laminated in two layers or more and being coupled each other by specific surface area as small as possible and a side surface part 8 constituted by fixing hard abrasive gain 7 which is smaller than a difference in level of thickness of the disc substrate 1 and the cutting edge layer by an electrodeposition on both the surfaces between the cutting edge part 5 and a substrate fastening part 6. In adhesion of abrasive grain 4 each other of the cutting edge part 5, the adhesion is performed with active silver braze of autosoluble alloy and a pore 11 with abrasive grain adhesive percentage of void of 10 to 50% is provided. Hard abrasive grain 7 of the side surface part 8 is dispersed and fixed in a geometric array shape or at random by mixing single or two kinds or more of prescribed abrasive grain. An alloy of a prescribed composition is used in the disc substrate 1.