To provide a moisture fluctuation estimation method for warehouse storage rice, capable of estimating and predicting long-term moisture fluctuations of the warehouse stored rice.

The moisture fluctuation estimation method includes the steps of dividing the inside of a warehouse 1, incorporating thermo-hygrometers, 2 into a plurality of adequate management sections A1 to Ax in which a temperature and humidity change behavior can be considered as being substantially identical; storing the warehouse stored rice packed in a specific style in each management section A1 to Ax, with the warehouse storage rice being management object samples R1 to Rx with a measured moisture Mo at warehousing; disposing an index sample 3 in the management section, the index sample having an initial measured mass Wo and an initial measured moisture Mo, and being put in a net basket 4; obtaining an equilibrium moisture me of the index sample 3, at an arbitrary time of measurement t, 24 hours after warehousing; obtaining, in advance, a diffusion coefficient κx indicating the moisture diffusion rate of the index sample 3; and estimating and computing each moisture level mt1, mt2, ..., and mtx of the management object samples in a sequential manner at each measurement t1, t2, ..., and tx.