We investigated the changes of granules in the attrition process during repeated pneumatic transport, along with the factors that affected these changes. Experiments were conducted with a shot-feed type dense phase pneumatic transporter, a device that allows a low rate of attrition by transporting granule lumps one by one. Easily attrited granulated materials were used. The analysis revealed an equation describing the relationship between the fine particle increment rate (named F) and the mass median diameter of coarse granules. The following results were obtained: (1) the degree of attrition was reduced with the increase in the fine particle ratio (mass fraction) before transport; and (2) the F value increased proportionally to the granule diameter.