To provide a fluid ejector which can perform image formation processing by ejection of a fluid to a target under a suitable processing condition in accordance with an image quality of images formed to the target without requiring a complicate controlling constitution.

A first unit head and a second unit head arranged adjoining the first unit head among a plurality of unit heads 24 which constitute a line head 13 are configured to be able to eject an ink to a paper P in a first arrangement mode which enables the heads to be arranged while separated in a conveyance direction of the paper P with an interval of an integral multiple of the peripheral length of a driving roller 18 spaced between nozzles of the first unit head and nozzles of the second unit head formed on positions corresponding in the conveyance direction of the paper P to the nozzles, and in a second arrangement mode which enables the heads to be arranged while separated in the conveyance direction of the paper P with a minimal interval spaced between nozzles of the first unit head and nozzles of the second unit head corresponding in the conveyance direction of the paper P to the nozzles.