A processing device comprising: a first reception portion (27, 35, 85) configured to receive, from a platen identification information portion provided on a platen, platen identification information (PID1~PID3) that identifies the platen, the platen being used in a printer and in a related device that is at least one of a pretreatment device and a post-treatment device; and a first processing portion (11, 31, 111) configured to perform processing in one of the printer and the related device, on the basis of the platen identification information received by the first reception portion. wherein the first reception portion receives (S12, S32, S52) the platen identification information that is associated with at least one of print content in the printer and processing content in the related device, and the first processing portion performs the processing (S23, S43, S58) content associated with the platen identification information; characterised in that the processing device further comprises: a second reception portion configured to receive print medium information of a print medium that is set on the platen; a third reception portion provided at a position on the same side as the second reception portion with respect to the first reception portion, and configured to receive the platen identification information from the platen identification information portion; and a first control portion (11,31,51,111) connected to the second reception portion and the third reception portion, wherein the first control portion performs association processing that associates the platen identification information received by the third reception portion with the print medium information received by the second reception portion. a first reception portion (27, 35, 85) configured to receive, from a platen identification information portion provided on a platen, platen identification information (PID1~PID3) that identifies the platen, the platen being used in a printer and in a related device that is at least one of a pretreatment device and a post-treatment device; and a first processing portion (11, 31, 111) configured to perform processing in one of the printer and the related device, on the basis of the platen identification information received by the first reception portion. wherein the first reception portion receives (S12, S32, S52) the platen identification information that is associated with at least one of print content in the printer and processing content in the related device, and the first processing portion performs the processing (S23, S43, S58) content associated with the platen identification information; characterised in that the processing device further comprises: a second reception portion configured to receive print medium information of a print medium that is set on the platen; a third reception portion provided at a position on the same side as the second reception portion with respect to the first reception portion, and configured to receive the platen identification information from the platen identification information portion; and a first control portion (11,31,51,111) connected to the second reception portion and the third reception portion, wherein the first control portion performs association processing that associates the platen identification information received by the third reception portion with the print medium information received by the second reception portion. a second reception portion configured to receive print medium information of a print medium that is set on the platen; a third reception portion provided at a position on the same side as the second reception portion with respect to the first reception portion, and configured to receive the platen identification information from the platen identification information portion; and a first control portion (11,31,51,111) connected to the second reception portion and the third reception portion, wherein the first control portion performs association processing that associates the platen identification information received by the third reception portion with the print medium information received by the second reception portion.