A method for arranging liquid droplet ejection heads includes: arranging and fixing a plurality of inkjet liquid droplet ejection heads, ejecting a common functional liquid, on a common carriage plate, based on the amount of liquid droplets ejected from a number of ejecting nozzles in a nozzle row that each of the liquid droplet ejection heads has, with the heads shifted in a direction of the nozzle row, the heads being so arranged and fixed that in the heads closely aligned in the direction of the nozzle row, a difference between the amounts of liquid droplets ejected from two ejection nozzles located at each innermost end of the heads is within a predetermined range of tolerance, and the amounts of liquid droplets ejected from two ejection nozzles located at the outermost ends in the direction of the nozzle row are within a predetermined range of a reference amount.