An additional conveyance mechanism of a printer, a first printing section, and a second printing section, wherein the additional conveyance mechanism of the printer apparatus comprises: a second paper conveyance path configured to convey papers having only one printing surface in which side it is merged with the first paper conveyance path between the first printing section and the second printing section, and a separation mechanism configured to separate the thermal printing head carrying out no printing from the platen roller in the contacted thermal printing heads and platen rollers when the papers loaded in the printer apparatus and the additional conveyance mechanism of the printer apparatus are printed.