To prepare a production instruction capable of preventing the absence of stock of products having the month-long fluctuation and that within a month in the fluctuation of orders.

This production instruction preparing system comprises a comparing means 31 for comparing the total amount of prepared instruction of production and the total amount of production plan for a specific period of the production plan by month and by a product number (hereinafter the total amount of production plan); a product number selecting means 32 for selecting a product number having high possibility of the absence of stock from the products free from the absence of stock in a case when the total amount of instruction of production of the products of the absence of stock is smaller than the total amount of production plan as the result of the comparison; an additional instruction of production preparing means 33 preparing the instruction of production of the selected product number to be added to the total amount of the instruction of production; and inputting the total amount of the instruction of production after the addition to the comparing means 31, and an output of instruction of production control means 34 repeating the processings by the comparing means 31, the product number selecting means 32 and the instruction of additional production preparing means 33 until the total amount of the instruction of production becomes larger than the total amount of the production plan.