To provide an electrodeposition thin blade tool manufacturing method superior in electrodeposition efficiency, and high in productivity, by performing stable processing with the long service life, by reducing a cutting margin.

A register mask 20 forming an opening part of the predetermined size, is applied to a side surface of base metal 12 of a disk-like and slender rectangular plate-like metallic thin plate. A recessed part 14 having a taper having a wide opening part by an opening part 20a, is formed on the base metal 12 by chemical treatment processing. A width of the wide opening part 14a of the recessed part 14 is formed larger than a diameter of an abrasive grain 16 and smaller than 2 times of its diameter. The abrasive grain 16 partially projecting from the recessed part 14 is stored in the recessed part 14, and the abrasive grain 16 in the recessed part 14 is fixed to the base metal 12 by electrodeposition.