The present invention is to provide a method and an apparatus for mounting components having a feature of detecting with high accuracy component pick up failure by the nozzle at component pick up stage, and/or component carrying back by the nozzle at component mounting stage. Achieved vacuum pressure is initialized to zero after completion of component pick up by the nozzle 25, and vacuum pressure decrease of the nozzle 25 is detected from the initialized zero point. If the detected value is bigger than the predetermined threshold, it may be judged that at least one of the nozzles failed to pick up a component. The failed nozzle may be identified by using a component recognition device 37. Blowing air blow volume flowing through the nozzle 25 is measured upon completion of component mounting. If the blowing air flow is smaller that the predetermined threshold, it is judged that the nozzle 25 carries back a component 30. Two thresholds may be used, and it may be judged that the component has been properly mounted if the measurement value is bigger than both thresholds, filter 22 is clogged if the measurement value is in between the two thresholds, and the nozzle 25 carries back the component if the measurement value is smaller than both thresholds.