An object of the invention is to provide an electronic component mounting system and an electronic component mounting method which can execute component mounting work on a plurality of boards simultaneously, concurrently and efficiently so that high productivity and responsiveness to production of many items can be achieved consistently.Provided is an electronic component mounting line (1) which is formed so that a screen printing portion having a plurality of individual printing mechanisms capable of executing setup change works individually is connected to an upstream side of a component mounting portion having a plurality of board delivery mechanisms, and which is configured so that either of a first work mode in which component mounting work is continuously executed on a fixed board type in all individual mounting lanes (L1 and L2) and a second work mode in which component mounting work is intermittently executed in one individual mounting lane while setup change work is repeated in corresponding one of the individual printing mechanisms whenever board types are changed from one to another in the individual mounting lane is selectively designated in multi-board mounting work in which the individual mounting lanes are operated to execute component mounting work on a plurality of boards simultaneously and concurrently.