PURPOSE: To reduce the production space, the stock of half-finished goods, the time for switching the kinds of machines so as to improve the productivity, in an electronic parts automatic mounting system for conducting transport, supply, housing, buffer, direction change and the like of a printed board.

CONSTITUTION: A printed board transport direction changing device 14 comprising a printed board transport conveyer portion for transporting a printed board in two directions and a rotating unit for rotating it and an elevating unit 12 for holding the rotating unit and positioning the same in the vertical direction are placed on a truck 8. One printed board transport wagon 16 which is loaded with the transport direction changing device 14 and the elevating unit 12 on its truck 8 and runs along a designated route 17 can supply and carry out a printed board, so that the number of printed board stockers can be reduced.