A bonding device for bonding substrates together, includes: a first holding unit configured to hold a first substrate on a lower surface thereof; a second holding unit located below the first holding unit and configured to hold a second substrate on an upper surface thereof; a moving mechanism configured to move the first holding unit or the second holding unit in a horizontal direction and a vertical direction; a first image pickup unit located in the first holding unit and configured to pick up an image of the second substrate held in the second holding unit; and a second image pickup unit located in the second holding unit and configured to pick up an image of the first substrate held in the first holding unit, at least one of the first image pickup unit and the second image pickup unit including an infrared camera.