Studies were processed to confirm the differences of productivity according to sawdust size and effect of additives for sawdust cultivation of shiitake. In results of investigation until shiitake mycelia fully spread on surface of sawdust medium, mycelial growth in treatment of sawdust size 3~5 mm with CaCO₃ and KNO₃, and treatment of sawdust sizw 3~5 mm without CaCO₃ and KNO₃ was the fastest. And, in investigation of rate of weight reduction, treatment of sawdust size below 1 mm without CaCO₃ and KNO₃ was the highest. The tendency of fruiting was somewhat different according to treatments. In case of sawdust size below 1 mm with CaCO₃ and KNO₃, yield produced from 1st to 2nd flushing period was over 80%. However, in case of sawdust size below 1 mm plus 5~7 mm without CaCO₃ and KNO₃, yield produced from 3rd to 4th flushing period was more than it from 1st to 2nd flushing period and rate of yield produced from 1st to 2nd flushing period to total yield was 34%. Results of investigation on productivity, yield and the number of fruit-bodies were remarkably different according to treatments. Sawdust size 3~5 mm with CaCO₃ and KNO₃, whose total yield and the number of fruit-bodies were 568 g and 67, respectively, was the highest. And, total yield of medium of sawdust size below 1 mm plus 2~3 mm without CaCO₃ and KNO₃ was lowest as 227 g and the number of fruit-bodies of medium of sawdust size below 1 mm plus 5~7 mm without CaCO₃ and KNO₃ was lowest as 24. In investigation on amount of fruit-bodies over 10 g, medium of sawdust size 3~5 mm with CaCO₃ and KNO₃ was highest as 397 g.