A light source device comprising: an optical fiber; a beam light source configured to coaxially combine a plurality of laser beams of different peak wavelengths to generate and emit a wavelength-combined beam; and an optical coupling device configured to allow the wavelength-combined beam emitted from the beam light source to be incident on the optical fiber, wherein the optical coupling device comprises: a first cylindrical lens configured to focus the combined beam in a first plane containing a propagation direction of the combined beam and a first direction that is orthogonal to the propagation direction, the first cylindrical lens having a first focal length (EFL SAF1); a second lens configured to focus the combined beam in a second plane containing the propagation direction and a second direction that is orthogonal to both the propagation direction and the first direction, the second lens having a second focal length (EFL FAF); and a third cylindrical lens configured to focus the combined beam in the first plane so as to be incident on the first cylindrical lens, the third cylindrical lens having a third focal length (EFL SAF2) greater than the first focal length (EFL SAF1), wherein a first beam parameter product of the wavelength-combined beam along a first direction, which is orthogonal to a propagation direction of the wavelength-combined beam, is greater than a second beam parameter product of the wavelength-combined beam along a second direction, which is orthogonal to both the propagation direction and the first direction, characterized in that - the second lens is a cylindrical lens, and - a distance (d 2) between the third cylindrical lens and the first cylindrical lens is shorter than the third focal length (EFL SAF2). an optical fiber; a beam light source configured to coaxially combine a plurality of laser beams of different peak wavelengths to generate and emit a wavelength-combined beam; and an optical coupling device configured to allow the wavelength-combined beam emitted from the beam light source to be incident on the optical fiber, wherein the optical coupling device comprises: a first cylindrical lens configured to focus the combined beam in a first plane containing a propagation direction of the combined beam and a first direction that is orthogonal to the propagation direction, the first cylindrical lens having a first focal length (EFL SAF1); a second lens configured to focus the combined beam in a second plane containing the propagation direction and a second direction that is orthogonal to both the propagation direction and the first direction, the second lens having a second focal length (EFL FAF); and a third cylindrical lens configured to focus the combined beam in the first plane so as to be incident on the first cylindrical lens, the third cylindrical lens having a third focal length (EFL SAF2) greater than the first focal length (EFL SAF1), wherein a first beam parameter product of the wavelength-combined beam along a first direction, which is orthogonal to a propagation direction of the wavelength-combined beam, is greater than a second beam parameter product of the wavelength-combined beam along a second direction, which is orthogonal to both the propagation direction and the first direction, characterized in that - the second lens is a cylindrical lens, and - a distance (d 2) between the third cylindrical lens and the first cylindrical lens is shorter than the third focal length (EFL SAF2). a second lens configured to focus the combined beam in a second plane containing the propagation direction and a second direction that is orthogonal to both the propagation direction and the first direction, the second lens having a second focal length (EFL FAF); and a third cylindrical lens configured to focus the combined beam in the first plane so as to be incident on the first cylindrical lens, the third cylindrical lens having a third focal length (EFL SAF2) greater than the first focal length (EFL SAF1), wherein a first beam parameter product of the wavelength-combined beam along a first direction, which is orthogonal to a propagation direction of the wavelength-combined beam, is greater than a second beam parameter product of the wavelength-combined beam along a second direction, which is orthogonal to both the propagation direction and the first direction, characterized in that - the second lens is a cylindrical lens, and - a distance (d 2) between the third cylindrical lens and the first cylindrical lens is shorter than the third focal length (EFL SAF2). - the second lens is a cylindrical lens, and - a distance (d 2) between the third cylindrical lens and the first cylindrical lens is shorter than the third focal length (EFL SAF2).