According to one embodiment, there is provided a laser ion source. The laser ion source includes a vacuum chamber which is vacuum-exhausted and in which a target is transported and set, a valve which is opened when the target is transported into the vacuum chamber and is closed except for the transportation, a target supply chamber which holds the target to be movable, and a transportation unit which transports to the vacuum chamber the target held on the target supply chamber while opening the valve after the target supply chamber is vacuum-exhausted while closing the valve.