Provided are a head device, an ink jet printing device, and a driving voltage adjustment method capable of adjusting a driving voltage corresponding to a target jetting amount and suppressing unevenness of printing density occurring between head modules. A dead device includes an ink jet head including a plurality of head modules, and a driving voltage supply device that includes a processor and supplies a driving voltage to the ink jet head, in which the processor acquires a module characteristic, acquires an ink characteristic of ink applied to printing, derives a first voltage coefficient for adjusting a driving voltage corresponding to a target jetting amount for each head module based on the module characteristic and the ink characteristic, and adjusts the driving voltage by applying the first voltage coefficient for each head module.