An ink jet printing method includes scanning a printing medium in a scanning direction a plurality of times with an ink jet head from which inks and a treatment liquid acting to flocculate constituents of the inks are ejected. The ink jet head includes first ink nozzles filled with a first ink and arranged in a sub-scanning direction, second ink nozzles filled with a second ink having a different composition from the first ink and arranged in the sub-scanning direction, and treatment liquid nozzles filled with the treatment liquid and arranged in the sub-scanning direction. At least some of the treatment liquid nozzles are coincident in the sub-scanning direction with the first and second ink nozzles. The first ink nozzles are closest to the treatment liquid nozzles in the scanning direction, and the first ink exhibits a viscosity increase by a factor of 6.0 or less.