A drive circuit for driving a plurality of nozzles to discharge ink droplets. The testing chart comprises a contrast chart including a first line segment group having first line segments formed by causing the drive circuit to output a reference drive signal for a density serving as reference, thereby to make discharge from a first number of driven nozzles, the first line segments extending in a direction perpendicular to a transport direction and arranged at predetermined intervals, and a second line segment group having second line segments formed by causing the drive circuit to output a drive signal for driving only a selected number of nozzles as target of correction less than the first number of driven nozzles, the second line segments being formed between the first line segments while changing the correction values for correcting the drive signal of the drive circuit.