In an inkjet printer, a controller is configured to calculate, during movement of a carriage in a scanning direction, a signal level difference between a first detection signal in a mountain peak zone including an assumed mountain peak position and the first detection signal in a valley bottom zone including an assumed valley bottom position identified, based on information stored in a storage, and alternately execute, during the movement of the carriage, an ejection process of ejecting ink drops, and a conveying process of conveying the sheet by a predetermined line feed width. In the printing process, the printing head and the conveyor are driven according to a first condition when the signal level difference is equal to or larger than a threshold value, while driven according to a second condition when the signal level difference is less than the threshold value.