This component mounter mounts a component on a mounting target. The component mounter comprises a mounting head and a detection device. The mounting head has a base part, a raising/lowering mechanism, a suction nozzle, an impelling part, and a valve. The base part has, on the inside thereof, a first gas passage and a second gas passage that do not communicate. The raising/lowering mechanism raises/lowers the base part. The suction nozzle has a nozzle part that is arranged below the base part, that rises and falls in association with the raising/lowering of the base part, and that suctions the component by means of negative pressure that has been supplied to the first gas passage. The impelling part impels the nozzle part downward but allows the nozzle part to be pressed toward the base part. When the nozzle part has been pressed a prescribed amount, the valve allows the second gas passage to communicate with the outside. The detection device detects the flow rate and/or pressure of gas flowing through the second gas passage.