An inkjet printer is configured to acquire gap variation information related to a variation of a gap between a specific portion of an ink discharging surface and a recording sheet as a function of an inkjet head position, the specific portion located within a usage nozzle disposed area where usage nozzle rows to be actually used are disposed, determine representative gap variation information related to a variation, as a function of the inkjet head position, of a representative gap representing actual gaps between the usage nozzle rows and the recording sheet, by multiplying the gap variation information by a correction coefficient dependent on a width of the usage nozzle disposed area in a head moving direction and a wavelength of a wave shape of the recording sheet, and determine ink discharging timing based on the representative gap variation information, assuming that the actual gaps are equal to the representative gap.