Annular grindstone and manufacturing method of annular grindstone

A manufacturing method of an annular grindstone which includes a grindstone portion in which abrasive grains are fixed with a bonding material containing nickel and has a through hole at a center thereof, the manufacturing method comprising:

• a plating bath preparation step of preparing a plating bath in which a nickel plating solution into which the abrasive grains are mixed and an additive which contributes to formation of a porous structure are stored;
• an immersion step of immersing a base and a nickel electrode in the plating bath;
• a grindstone portion forming step of flowing a direct current through the plating solution with the base as a cathode and the nickel electrode as an anode, thereby depositing a plating layer containing the abrasive grains on a front surface of the base to form the grindstone portion;
• and
• a base removing step of removing all or part of the base to expose all or part of a region of the grindstone portion which is covered with the base,
• wherein, in the grindstone portion forming step, a first layer and a second layer having a porous structure are caused to be alternately laminated on top of another by alternately changing a current density of the direct current between a current density smaller than a predetermined value and a current density of the predetermined value or more, thereby forming the grindstone portion having a laminated structure of a total of three or more layers in which both of outermost layers which are exposed outside are the first layers.