Flushing timing adjustment method and inkjet recording device

An ink jet recording device, comprising:

• a recording head having a plurality of nozzles for discharging ink;
• an endless conveyance belt that conveys a recording medium and has openings at a plurality of locations in the conveyance direction of the recording medium, the openings allowing ink to pass through when the recording head executes flushing for discharging the ink at timing different from timing that contributes to image formation;
• a recording medium supply portion that supplies the recording medium to the conveyance belt;
• a recording medium detection sensor that detects the recording medium supplied from the recording medium supply portion to the conveyance belt;
• an opening detection sensor that detects the openings that move by running of the conveyance belt, and also detects the recording medium on the conveyance belt;
• and
• a discharge control portion that controls the ink discharge from the recording head, wherein
• the discharge control portion causes a first chart to be recorded on the recording medium by discharging ink from a predetermined nozzle of the recording head at a plurality of discharge timings set in advance using a detection time point at which the recording medium is detected by the recording medium detection sensor as a reference time point, and causes a second chart to be recorded on the recording medium alongside the first chart by discharging ink from another nozzle of the recording head at a plurality of discharge timings set in advance using a detection time point at which the recording medium is detected by the opening detection sensor as a reference time point.