A spray system has a base plate, a support member, a first cylinder mechanism and a second cylinder mechanism, a first slide tube and a second slide tube, a first board portion and a second board portion, a first holding bar, and a second holding bar. Each board portion is so constructed that a nozzle cassette is detachably fitted to a board base plate, the nozzle cassette is equipped with a number of spray nozzles, the first cylinder mechanism is so constructed that the first board portion can be moved relative to the support member, and the second cylinder mechanism is so constructed that the second board portion can be moved relative to the support member.