PURPOSE: To dissolve a problem, in a pneumo-electric control type ink jet recorder, that the distance between adjacent heads is varied depending on the fixing accuracy of head and the dots are superposed while being shifted.

CONSTITUTION: A pressure detection part 11 is provided to a fixed platen 1 oppositely to a scan locus of air discharge opening 12-15 of respective heads 6-9, each of which measures an interval between pulses outputted from the pressure detection part 11 by an air flow when the air discharge openings 12-15 are opposed respectively to the pressure detection part 11 by counting a pulse outputted from a linear scale reader part 4 as an accurate distance between the heads. Those values are stored in a CPU or the like and superposition of dots is accurately performed by adjusting discharge timing.