An electronic circuit component mounter equipped with a moving type component supply device which supplies electronic circuit components to a component holding tool and which is moved together with the component holding tool. In a state with passage-equipped component case is attached to the head main body, a dropped component catch plate is positioned below the rotational axis path of a suction nozzle and catches dropped components, while the raising/lowering of the suction nozzle is allowed at the component mounting position by opening and components are mounted on a board. Further, a sheet is affixed that prevents the movement of dropped components, and a dropped component catch plate is attached/detached to/from the head main body together with passage-equipped component case, and dropped components are removed in a state removed from the head main body.