machine and so on into consideration if each head unit contains dummy nozzles the largest possible number may not be exactly dividable by the integer n then the number of nozzles may be determined to be equal to an integer close to the quotient obtained by dividing the largest possible number by the integer n with the color ink jet head 1 having the above described configuration four head units are arranged in a direction perpendicular to the printing direction of the ink jet head for each of the ink colors of black b yellow y magenta m and cyan c although the head units of a same color may be separated considerably in the printing direction and all the nozzles are arranged at a same and identical pitch of p therefore a cycle of printing operation is carried out properly with a width substantially equal to that of four head units arranged side by side when the timing of ejection of ink of each color from the nozzles of each head unit is properly controlled thus a high speed printing machine can be realized by using this embodiment of color ink jet head according to the invention there may be cases where dummy nozzles are used then the total number of nozzles may not be exactly dividable by n and equal to 402 for ink of each color for instance however no problem arises when n 4 is used for such a case as pointed out above all the head blocks have a same and identical configuration therefore if the color ink jet head is made to comprise three head blocks by removing a head block from the above described embodiment of color ink jet head.