To provide a printer device capable of detecting a conveying state of feeding and discharging a recording paper and capable of judging if a length of the fed recording paper is within a predetermined criterion or not with a simple structure by using sensors constituted alone for the printer device to have the recording paper moved in a reciprocating motion to have a paper feeding part and a paper discharging part mounted on the same side as a printed part.

In the printer device having the feeding part and the discharging part mounted on the same side as the printed part to have the recording paper moved in a reciprocating motion, a passage for feeding and a passage for discharging can be easily switched at the time of feeding and at the time of discharging by using a non-returning member 38, and detecting means 65, 35c2, 37a capable of detecting both that a tip part of the recording paper 33 is fed near the passage for feeding on the printed part side than the non-returning member 38 in a direction of the printed part and that a rear end of the recording paper 33 is discharged in a direction of the passage for discharging are mounted therein.