A printer apparatus includes a print head, a platen roller, and a frame, wherein printing is performed on recording paper situated between the print head and the platen roller, wherein a projection is formed at a side face of the print head, wherein a side face of the frame has a groove formed therein for receiving the projection, wherein the groove includes a first area constituting an entrance to the groove, a second area for positioning the projection and formed such as to extend in a direction intersecting with a direction in which the first area extends, and a slanted part formed between the first area and the second area, and wherein the slanted part is an edge of the groove and extends in a direction different from both a direction in which the projection moves in the first area and a direction in which the projection moves in the second area.