A label sheet conveyance device is provided to more accurately automatically detect seams between label sheets in a label printer.Using a first threshold value that is set according to the mode of sensor output values for detecting the sheet portion between labels, and a second threshold value that is greater than the first threshold value for detecting holes in the label sheet, a label printer determines a sheet position where the sensor output value is equal to each threshold value. If a sheet position equal to the second threshold value is detected, the center of that sheet position is identified as the seam position. If a sheet position equal to the second threshold value is not identified and a sheet position equal to the first threshold value is identified, the center of that sheet position is identified as the seam position.