A linear gage includes a spindle, a guide cylinder surrounding a portion of the spindle and configured to guide the spindle to move forward and rearward in an axis line direction, and a guide slit portion having a guide slit extending parallel to the axis line of the guide cylinder, with a gap provided between the guide slit and an outer surface of the guide cylinder. An attitude adjustment pin extends into the guide slit and is fixed to a side surface of the spindle. The attitude adjustment pin is an eccentric pin.