A Littrow-type external-cavity diode laser optical axis displacement correction method and device to easily, inexpensively, and accurately correct displacement of optical axis in Littrow-type ECDLs is provided. In the Littrow-type ECDL optical axis displacement correction device and method, a means for introducing a laser beam, a jig 36 for integrally fixing a diffraction grating 33 and a prism 35 into which the laser beam is introduced in a predetermined arrangement, and a rotary shaft 34 capable of integrally rotating the diffraction grating 33 and the prism 35 are included. By the rotation of the diffraction grating 33 and the prism 35 around the rotary shaft 34, the wavelength of the incident light can be changed, and the optical axis of the output light 39 is not changed by the change of the wavelength.