A system for manufacturing an assembly board includes an undersupporting device, a transporter configured to transport a board and the undersupporting device, an undersupporting-device installer provided below the transporter, the undersupporting-device installer being attachable to and detachable from the undersupporting device, a board processor configured to perform a predetermined processing to an upper surface of the board, a carry-in side delivering unit having first and second receiving positions different from each other, a board supplier configured to supply the board to the first receiving position, and an undersupporting-device supplier configured to supply the undersupporting device to the second receiving position. The transporter transports, to the carry-in side delivering unit, the undersupporting device detached from the undersupporting-device installer. The carry-in side delivering unit positions, at the second receiving position, the undersupporting device delivered from the transporter to allow the undersupporting device to be carried out from the second receiving position.