Abstract: Electronic components such as chips are attracted to the tip ends of nozzles under suction, and mounted on printed-circuit boards when the vacuum condition in the nozzles is broken. The time for breaking the vacuum condition in the nozzles is adjusted by a variable time adjusting unit based on angular displacement information of a cam which vertically moves the nozzles depending on the selected mounting cycle. Even when a different mounting cycle is selected, time delays are varied to adjust the time for breaking the vacuum condition in the nozzles for thereby-mounting electronic components accurately and stably on printed-circuit boards.