PURPOSE: To optimally regulate an elevation stroke of a nozzle and to effectively place an electronic component on a board by measuring the height of the lower surface of the board at an electronic component placing position.

CONSTITUTION: X-Y tables 3, 4 are driven to move a transfer head 5 in X-Y directions to place an electronic component P on a board 1. Here, before a nozzle 6 is vertically moved to place the component on the board, the height of the lower surface of the placing position is measured by a measuring unit 7. Since the thickness of the board is already known, the thickness of the board is added to the height of the lower surface to discover the height of the placing position of the board. The vertical stroke of the nozzle is controlled to become an optimum stroke based on the measured result, and the component is placed on the board.