To quickly wash off the residue by directly and concentrately supply a solvent to a blade of a cutter.

An adaptor 4.1 is provided with a conduit 5.2 for supplying a cooling agent and a lubricant. The solvent is radially outwardly supplied to a blade of a cutter 2.1 from a radial inside through a conductor comprising the conduit part 5.2 in the adaptor 4.1 and a conduit part 5.3 in a grinding disc 4.2. To increase the pressure, a plurality of backets are mounted. These buckets are used to increase the pressure. The buckets may be also formed as pump buckets. First of all, the cooling agent and the lubricant reach the conduit part 5.2 through the conduit 5.1. The acceleration is generated by the centrifugal force when they are transferred from the conduit 5.1 to the conduit part 5.2, whereby the pressure is increased.