To provide a method and a device for manufacturing a metal mold with high machining accuracy and production efficiency for molding a honeycomb structure.

In a method for manufacturing a metal mold for forming a honeycomb structure, which has a supply hole for supplying material and slit grooves communicated with the supply hole and used for forming the material into a honeycomb shape, the machining of the slit grooves 82 is performed by repeatedly electrically machining a groove forming surface 89 of a metal mold-ray material 80 in a working fluid, using a pipe-like machining electrode 1 having the same cross section as one grid of the honeycomb.