The present invention provides an attachment angle measuring device and an attachment angle measuring method which realize accurate measurement of attachment angle between an axle carrier and an absorber. An attachment angle measuring device measures an attachment angle θ between an axle carrier and an absorber as in the following. A slit light is projected to a first reflection position on an outer peripheral surface of an absorber rod and a reflected light from the first reflection position is received. A slit light is projected to a second reflection position on the outer peripheral surface of the absorber rod different from the first reflection position and a reflected light from the second reflection position is received. A first optical path distance between a projection start position of the slit light and the first reflection position is calculated based on the reflected light. A second optical path distance between the projection start position of the slit light and the second reflection position is calculated based on the reflected light. Based on the first optical path distance and the second optical path distance, attachment angle θ is calculated.