1. The primary object of harrowing on paddy-field. is to make the field in suitable condition to transplant rice plants, and the secondary is to reduce the loss of water by percolation. 2. The effects of harrowing are made of the follwing processes : (1) breaking up the clods, (2) stirring the soil, (3) repressing the soil, (4) making the land level, (5) compressing the furrow bottom and filling the holes in there. 3. Spike harrows "Maguwa", "Shiroguruma", Rotary cutaway disc harrows, "Conpeto" harrows and "Shirozuki" , studied in this treatise, have very different function of harrowing respectively. 4. The selection and using of harrows should be done in order to gain the. chief object of harrowing in compliance with the physical properties of the soil.