To shorten the reciprocating time of a moving body in a liquid ejector which is equipped with a plurality of nozzle groups for ejecting a liquid to a medium during the reciprocation of the moving body.

This liquid ejector is equipped with the moving body which reciprocates in a predetermined moving direction, and the plurality of nozzle groups which is held by the moving body so as to eject the liquid to the medium during the reciprocation; the plurality of nozzle groups are arranged in the moving body from one end to the other end in the moving direction; the moving body has a plurality of sensors for detecting the medium; and either a liquid ejection starting position or a liquid ejection completing position is determined according to the result of detection. The liquid ejector is characterized as follows: one of the plurality of sensors is provided on the side nearer to the other end than the nozzle group arranged on the side nearest to one end in the moving direction; and the other one of the sensors is provided on the side nearer to one end than the nozzle group arranged on the side nearest to the other end.