PURPOSE: To provide a work instruction system for an assembly line preventing an increase in the amount of information to be saved in obtaining work instruction information at each process regarding each type of products.

CONSTITUTION: One product is selected as a basic product from a plurality of products, and work instruction information at the time of assembling the basic product is saved as a basic layout drawing in a basic layout drawing memory section 2. In addition, a correlation between the work instruction information on a product to be assembled and the basic layout drawing is saved as an identification code in an identification code memory section 2. According to an identification code as read out, a work instruction information operation section 5 is caused to perform the rotation or reversal, or the combination thereof, regarding the basic layout drawing as read out, thereby providing work instruction information corresponding to the product to be assembled.