The method to plan the column interval dimensions at Horyuji Kondo (the main hall of Horyuji temple) has been argued for a century. However we still have not reached to a reliable conclusion yet. This thesis explains the planning method of the column interval dimensions of Horyuji Kondo by adopting the mediaeval period's 'shiwarisei' as a clue.This is the method to design the standard unit of the column interval from the dimensions of the rafter interval. Up to the present, the method to plan the column interval dimensions at the Kondo has been understood by applying a whole number among the center of the columns. But fractional numbers happen to appear because of the existence of the interval dimensions of eaves girders (gagyou) and rafters.As a result, the existence of the primitive 'shiwari-sei' and a new planning method to position the columns can be proposed.