An inkjet image forming apparatus which is provided with a line engine in which one or more recording heads are aligned in a main scanning direction and which has replacably configured an arbitrary one of the recording heads is disclosed. In the inkjet image forming apparatus, each of the recording heads includes a head tank mounted on the recording head, the head tank including a supply port and a discharge port for ink, the head tanks which are adjacent are mutually connected by a path in which the discharge port and supply port of the respective head tanks are coupled via a coupling unit, a path from the discharge port and a path to the supply port differ in an inner path diameter over the coupling unit, and the inner path diameter on the discharge port side is larger than the inner path diameter on the supply port side.