Position detection device, position detection method, and vapor deposition apparatus capable of improving the detection accuracy of the position of a substrate

The present invention provides a position detection device, a position detection method, and a vapor deposition apparatus capable of improving the detection accuracy of the position of a substrate. An image processing part 20 calculates the relative position between the cameras 11 of a surface photographing part based on the result of photographing the substrate mark Wm by each camera 11 of the surface photographing part, calculates the position of a processing substrate W photographed from the surface based on the result of the relative position between the cameras 11 and using each camera 11 of the surface photographing part to photograph the processing substrate W, calculates the relative position between the cameras 12 of a back side photographing part based on the result of photographing the image of the substrate mark Wm by each camera 12 of the back side photographing part, and calculates the position of the processing substrate W photographed from the back side based on the result of the relative posi