A liquid ejection apparatus, comprising: a head (1, 2) which has a plurality of ejection openings for ejecting liquid, the ejection openings being arranged at equal intervals relative to one direction; a conveyor adapted for conveying a recording medium relatively to the head (1,2), in a conveyance direction intersecting the one direction; an image dot controller adapted to control the head (1,2) based on image data so that the liquid is ejected from the ejection openings to form image dots structuring pixels of an image on the recording medium conveyed by the conveyor; a determiner adapted to successively determine, for each of the ejection openings, whether an image dot non-forming period is equal to or longer than a predetermined time period, the image dot non-forming period being a period from a first time point where an image dot is formed to another time point where a subsequent image dot is formed under control by the image dot controller; and a non-image dot controller adapted to control the head (1, 2) so that each of the ejection openings, whose image dot non-forming period is equal to or longer than the predetermined time period, ejects the liquid once within a non-image dot forming period in the image dot non-forming period, to form on the recording medium a non-image dot which is not based on the image data, the non-image dot forming period being a period from a third time point which is after the first time point to a second time point which is the predetermined time period after the first time point, and that a plurality of the non-image dots structured by the liquid ejected from the ejection openings are scattered in the conveyance direction, characterized by that the head (1,2) includes a first head which eject a first liquid, and a second head positioned upstream of the first head relative to the conveyance direction, which ejects a second liquid containing a component to aggregate pigment of the first liquid or to precipitate dye of the first liquid; and the non-image dot controller is adapted to control the first and second heads so that the non-image dot related to the first head and the non-image dot related to the second head are formed in different positions of a recording medium. a head (1, 2) which has a plurality of ejection openings for ejecting liquid, the ejection openings being arranged at equal intervals relative to one direction; a conveyor adapted for conveying a recording medium relatively to the head (1,2), in a conveyance direction intersecting the one direction; an image dot controller adapted to control the head (1,2) based on image data so that the liquid is ejected from the ejection openings to form image dots structuring pixels of an image on the recording medium conveyed by the conveyor; a determiner adapted to successively determine, for each of the ejection openings, whether an image dot non-forming period is equal to or longer than a predetermined time period, the image dot non-forming period being a period from a first time point where an image dot is formed to another time point where a subsequent image dot is formed under control by the image dot controller; and a non-image dot controller adapted to control the head (1, 2) so that each of the ejection openings, whose image dot non-forming period is equal to or longer than the predetermined time period, ejects the liquid once within a non-image dot forming period in the image dot non-forming period, to form on the recording medium a non-image dot which is not based on the image data, the non-image dot forming period being a period from a third time point which is after the first time point to a second time point which is the predetermined time period after the first time point, and that a plurality of the non-image dots structured by the liquid ejected from the ejection openings are scattered in the conveyance direction, characterized by that the head (1,2) includes a first head which eject a first liquid, and a second head positioned upstream of the first head relative to the conveyance direction, which ejects a second liquid containing a component to aggregate pigment of the first liquid or to precipitate dye of the first liquid; and the non-image dot controller is adapted to control the first and second heads so that the non-image dot related to the first head and the non-image dot related to the second head are formed in different positions of a recording medium.