A solid laser apparatus which includes: two reflection elements for forming an oscillator; a plate-shaped gain medium being disposed between the two reflection elements, thereby augmenting a stimulated emission light in a thickness-wise direction; a doughnut- or deformed-doughnut-type planar waveguide being disposed so as to make an inner peripheral face thereof come in contact with an outer peripheral face of the plate-shaped gain medium; and a plurality of excited-light sources being directed in five or more directions, the excited-light sources being coupled to an outer peripheral face of the doughnut- or deformed-doughnut-type planar waveguide so as to make excited lights propagate from the outer peripheral face of the doughnut- or deformed-doughnut-type planar waveguide to the plate-shaped gain medium.