An image forming apparatus includes a carriage configured to movably scan, and including a recording head configured to discharge ink droplets and a sub tank configured to supply ink to the recording head; a main tank configured to supply the ink to the sub tank via a tube; a negative pressure detector configured to detect a state of a negative pressure in the sub tank; a count unit configured to count a number of scans conducted by the carriage; and a control unit configured to cause the negative pressure detector to detect the state of the negative pressure in the sub tank to return the negative pressure in the sub tank to a normal state based on a detection result obtained by the negative pressure detector when the number of scans carried out by the carriage as counted by the count unit reaches a predetermined scan count.