To provide a position detecting device and a position detecting method capable of easily detecting the displacement of a printing medium.

This position detecting device includes a paper edge detecting means 58 movable with a printing head 48 for detecting an edge of the paper, and a linear encoder 52 capable of detecting a position in the scanning direction of the printing head 48. A paper position is detected on the basis of results of detections by the paper edge detecting means 58 and the linear encoder 52, and the displacement of the paper is detected on the basis of a result of the detection of the paper position.