When an inkjet printer ejects ink onto a recording medium on a go path and on a return path of a carriage, if ink cannot be ejected onto the same position on the go path and on the return path, image quality becomes poor. Test patterns with shifted ejection timing are hitherto recorded on the recording medium, and appropriate timing is input as a correction value. There is also an inkjet printer which automatically reads a test pattern, but the test pattern is recorded without consideration of a state of a head, and thus, accuracy is low. Therefore, a test pattern having a long period and a test pattern having a short period are recorded, and densities of the test patterns are read by a sensor. An extremum candidate is determined from the test pattern having a long period, and rough adjustment is made first. Then, in a region around the extremum, an extremum is determined from the test pattern having a short period. An extremum corresponding to a period to which the extrema of the two test patterns belong is set as a correction value. By determining ejection timing of the recording head using the correction value, an image in which dot deviation between the go path and the return path is inhibited can be recorded.