A solid-state laser crystal constituting a laser-diode-excited solid-state laser apparatus or an optical fiber constituting a fiber laser apparatus or fiber laser amplifier is doped with one of Ho.sup.3+, Sm.sup.3+, Eu.sup.3+, Dy.sup.3+, Er.sup.3+, and Tb.sup.3+ so that a laser beam is emitted from the solid-state laser crystal or the optical fiber, or incident light of the fiber laser amplifier is amplified, by one of the transitions from .sup.5S.sub.2 to .sup.5I.sub.7, from .sup.5S.sub.2 to .sup.5I.sub.8, from .sup.4G.sub.5/2 to .sup.6H.sub.5/2, from .sup.4G.sub.5/2 to .sup.6H.sub.7/2, from .sup.4F.sub.3/2 to .sup.6H.sub.11/2, from .sup.5D.sub.0 to .sup.7F.sub.2, from .sup.4F.sub.9/2 to .sup.6H.sub.13/2, from .sup.4F.sub.9/2 to .sup.6H.sub.11/2, from .sup.4S.sub.3/2 to .sup.4I.sub.15/2, from .sup.2H.sub.9/2 to .sup.4I.sub.13/2, and from .sup.5D.sub.4 to .sup.7F.sub.5. The above solid-state laser crystal or optical fiber is excited with a GaN-based compound laser diode.