A radiation image reading device comprising: a light scanning unit configured to scan excitation light to a surface of a recording medium having a radiation image recorded thereon along a scan line; a light detection unit configured to detect signal light emitted from the surface of the recording medium (IPa) by the scanning of the excitation light within a detection surface intersecting the surface of the recording medium (IPa) and including the scan line; and an optical filter which is disposed between the light detection unit and the surface of the recording medium (IPa), characterized in that each of a transmittance when the excitation light reflected from the surface of the recording medium (IPa) is transmitted through the optical filter and a transmittance when the signal light emitted from the surface of the recording medium (IPa) at an angle larger than a predetermined angle with respect to a direction perpendicular to the scan line within the detection surface is transmitted through the optical filter is smaller than a transmittance when the signal light emitted from the surface of the recording medium (IPa) at an angle smaller than the predetermined angle with respect to a direction perpendicular to the scan line within the detection surface is transmitted through the optical filter; wherein the width of a detection region of the signal light is longer than the width of a scan region of the excitation light on the surface of the recording medium (IPa) within the detection surface, and wherein the predetermined angle is equal to or less than an angle formed by an imaginary line connecting one end of the scan region and one end of a detection region with respect to a direction perpendicular to the scan line within the detection surface. a light scanning unit configured to scan excitation light to a surface of a recording medium having a radiation image recorded thereon along a scan line; a light detection unit configured to detect signal light emitted from the surface of the recording medium (IPa) by the scanning of the excitation light within a detection surface intersecting the surface of the recording medium (IPa) and including the scan line; and an optical filter which is disposed between the light detection unit and the surface of the recording medium (IPa), characterized in that each of a transmittance when the excitation light reflected from the surface of the recording medium (IPa) is transmitted through the optical filter and a transmittance when the signal light emitted from the surface of the recording medium (IPa) at an angle larger than a predetermined angle with respect to a direction perpendicular to the scan line within the detection surface is transmitted through the optical filter is smaller than a transmittance when the signal light emitted from the surface of the recording medium (IPa) at an angle smaller than the predetermined angle with respect to a direction perpendicular to the scan line within the detection surface is transmitted through the optical filter; wherein the width of a detection region of the signal light is longer than the width of a scan region of the excitation light on the surface of the recording medium (IPa) within the detection surface, and wherein the predetermined angle is equal to or less than an angle formed by an imaginary line connecting one end of the scan region and one end of a detection region with respect to a direction perpendicular to the scan line within the detection surface.