PURPOSE: To obtain the titled MISO which can be stored without causing darkening of surface, by putting an oxygen-impermeable bag into a corrugated fiberboard box, charging a MISO raw material into the bag, closing the bag, placing a weight on the bag and closing the corrugated fiberboard box.

CONSTITUTION: A double bag composed of an oxygen-impermeable inner bag 2 and an outer bag 3 made of e.g. vinyl resin is placed in a corrugated fiberboard box 1 and a MISO raw material is put into the bag 2. The bag 2 is closed and weighted with a weight 4. The outer bag 3 is closed keeping the weight 4 therein and the lid of the corrugated fiberboard box 1 is closed to obtain the objective MISO. The weight is preferably produced by wrapping granules with a sheet.