A substrate attachment/detachment device which clamps and holds a substrate by means of first and second retaining members of a substrate holder, the device comprising a first holder retainer configured to hold the first retaining member in a first posture; and a second holder retainer configured to be movable in a linear manner toward and away from the first holder retainer, capable of holding the second retaining member in the first posture and a second posture which is substantially orthogonal to the first posture, configured to push the second retaining member against the first retaining member in the first posture to lock the first and second retaining members to each other.