A method for driving an inkjet head which applies a driving signal to pressure generator for expanding or contracting a capacity of a pressure chamber (30, 31, 32, 33, 34), applies a pressure to a liquid in the pressure chamber (30, 31, 32, 33, 34) by driving the pressure generator and ejects droplets from a nozzle, wherein when at least two droplets are ejected from the same nozzle and joined immediately after ejection so as to form a large droplet, a first driving signal is applied as the driving signal; the first driving signal has a first expansion pulse for expanding the capacity of the pressure chamber (30, 31, 32, 33, 34) and contracting it after certain time, a first contraction pulse for contracting the capacity of the pressure chamber (30, 31, 32, 33, 34) and expanding it after certain time, a second expansion pulse for expanding the capacity of the pressure chamber (30, 31, 32, 33, 34) and contracting it after certain time, and a second contraction pulse for contracting the capacity of the pressure chamber (30, 31, 32, 33, 34) and expanding it after certain time in this order; a first droplet is ejected from the nozzle by applying the first expansion pulse and the first contraction pulse and a second droplet is ejected by applying the second expansion pulse and the second contraction pulse; and a pulse width of the first expansion pulse is 0.4 AL or more and 2.0 AL or less, where AL is 1/2 of an acoustic resonant period of a pressure wave in the pressure chamber (30, 31, 32, 33, 34); wherein the first contraction pulse consecutively falls without a pause period from a terminal end of falling of the first expansion pulse, the second expansion pulse consecutively rises without a pause period from a terminal end of rising of the first contraction pulse, and the second contraction pulse consecutively falls without a pause period from a terminal end of falling of the second expansion pulse. when at least two droplets are ejected from the same nozzle and joined immediately after ejection so as to form a large droplet, a first driving signal is applied as the driving signal; the first driving signal has a first expansion pulse for expanding the capacity of the pressure chamber (30, 31, 32, 33, 34) and contracting it after certain time, a first contraction pulse for contracting the capacity of the pressure chamber (30, 31, 32, 33, 34) and expanding it after certain time, a second expansion pulse for expanding the capacity of the pressure chamber (30, 31, 32, 33, 34) and contracting it after certain time, and a second contraction pulse for contracting the capacity of the pressure chamber (30, 31, 32, 33, 34) and expanding it after certain time in this order; a first droplet is ejected from the nozzle by applying the first expansion pulse and the first contraction pulse and a second droplet is ejected by applying the second expansion pulse and the second contraction pulse; and a pulse width of the first expansion pulse is 0.4 AL or more and 2.0 AL or less, where AL is 1/2 of an acoustic resonant period of a pressure wave in the pressure chamber (30, 31, 32, 33, 34); wherein the first contraction pulse consecutively falls without a pause period from a terminal end of falling of the first expansion pulse, the second expansion pulse consecutively rises without a pause period from a terminal end of rising of the first contraction pulse, and the second contraction pulse consecutively falls without a pause period from a terminal end of falling of the second expansion pulse.