A control method of an ink jet printer having an ink jet head which ejects an ink droplet to record a dot on a recording sheet. When plural colors of ink are overlapped to record a dot, each color ink ejection time length is set shorter as compared with when a single-color dot is recorded. Ink amount in the dot in which the plural colors are overlapped is reduced, and ink blur on the recording sheet is prevented from occurring, so that recorded image quality can be enhanced. Preferably, ejection time width of one dot of ink ejected from the ink jet head is divided into plural pitches, each pitch is associated with an address of a timing data memory, and timing data is prepared by storing data indicating plural ejection time lengths of the ink jet head in the address corresponding to an ejection timing. Selection information for selecting any one of the ejection time lengths is included in record data for each dot, the ejection timing for each dot is determined from the timing data based on the ejection time length selected by the selection information of the record data, and each dot ink ejection time length is controlled.