Printing apparatus and method obtaining appropriate code size for medium type based on results of trial printing group of different sized codes

A printing apparatus includes a transport unit, a printing unit, a reading unit, and a control unit configured to control the transport unit and the printing unit to perform first printing processing and second printing processing, wherein the control unit prints, in the first printing processing, a code group including a first code of a first size and a second code of a second size larger than the first size on a first medium that is the medium, acquires reading data that is a result of reading, by the reading unit, of the code group printed on the first medium, determines a code size to be adopted for the second printing processing based on the reading data, and, in the second printing processing, prints a third code of the code size on a medium of the same type as that of the first medium.