An electronic component mounting method is performed by an electronic component mounting system including a component mounting line formed by interconnecting component mounting units which concurrently performs component mounting work on two kinds of boards different in mounting workload. The component mounting units includes: first and second board conveyance mechanisms; a component mounting unit; a board distribution unit which receives the board from the upstream-side apparatus and distributes the received board to either the first board conveyance mechanism or the second board conveyance mechanism; and a distribution control unit which controls the first board conveyance mechanism, the second board conveyance mechanism and the board distribution unit. The electronic component mounting method comprises mixedly distributing the two kinds of the boards to each of the first and second board conveyance mechanisms based on a board request signal issued from a most-upstream component mounting unit in the component mounting line.