To provide a printing apparatus capable of obtaining high image quality in a printing result even in the case carriage speed change is generated, a printing controlling unit and a printing irregularity adjusting method.

The printer 1 comprises a CPU 30 for controlling the entire apparatus, and a PROM 31 with a variable value table 42 stored. The CPU 30 starts ink ejection at a predetermined carriage position, triggered by the pulse of a detection signal outputted from a detection sensor 20 of a linear encoder 18 so as to eject the ink by a predetermined time interval (cycle). Moreover, the variable value table 42 of the PROM 31 stores a plurality of variable values (a) as the speed variable information for ejecting the ink by a timing different from an ordinary timing. The CPU 30 executes a process for changing the ink ejection timing of a predetermined path, using the valuable values (a) of the variable value table 42.