An adjustment pattern, which is composed of a reference pattern made of plural independent liquid droplets and a pattern to be measured made of plural independent liquid droplets ejected under an ejection condition different from the reference pattern, is formed on a water-repellent conveying belt. Then, light is applied to the adjustment pattern to receive the regular reflection light from the adjustment pattern, so that the adjustment pattern is scanned. The distance between the respective patterns is measured based on the measured result. Finally, liquid droplet ejection timing of the recording head is corrected based on the result thus measured.