grain size frequency array e5 is constituted by center grain size frequencies e5 1 to e5 n corresponding to different center grain sizes and the cumulative yield array e6 is constituted by cumulative yields e6 1 to e6 n respectively corresponding to the center grain size frequencies e5 1 to e5 n the initial values of the center grain size frequencies e5 1 to e5 n and cumulative yields e6 1 to e6 n are 0 fig3 to 5 show processing performed by the control computer 16 in which fig3 shows the overall processing sequence fig4 shows a sequence of obtaining initial value setup processing of fig3 and fig5 shows a sequence of target value change processing of fig3 the operation of the control computer 16 concerning automatic material loading amount control will be described in detail with reference to fig3 and 5 when a granular compound fertilizer of a certain brand is to be manufactured a predetermined amount of material is loaded by a manual operation to start the rotary granulator 1 and the control computer 16 starts processing shown in fig3 the control module 22 of the control computer 16 performs initial value setup processing s1 in the processing s1 as shown in fig4 the brand file 26 corresponding to the brand to be controlled is opened s11 since data representing a center grain size providing the maximum yield in the past and its maximum yield are stored in the brand file 26 these data are read out from the brand file 26 s12 and data representing a target center grain size.