Computer simulation by a two-dimensional random addition model was proposed to elucidate the mechanisms of granule growth and compaction process of agitation fluidized bed granulation. In this paper, adhesion force by liquid bridge and separation force by agitator rotation were taken into consideration for adhesion probability of colliding granules. Effects of moisture content and agitator rotational speed on granule diameter, shape and internal structure were investigated theoretically. This simulation was applied to actual granulation, in which lactose and corn starch mixed in a weight ratio of 7:3 were granulated by an aqueous solution of hydroxypropylcellulose. Close agreement between simulated and experimental results was obtained.