A laser plumbing device including a laser beam emitting device; a supporting device for supporting the laser beam emitting device and allowing swinging movements of the laser beam emitting device in a first direction X1 and a second direction Y1; a two-direction drive device for swinging the laser beam emitting device in the first and second directions X1 and Y1; an inclination angle detecting device for detecting an inclination angle of the laser beam emitting direction with respect to the vertical direction; and a controller for controlling the position of the laser beam emitting device by the two-direction drive device so as to change the laser beam emitting direction toward the vertical direction based on the angle detected by the inclination angle detecting device. The long member plumbing device and method utilizing the laser plumbing device.