A lawn mower includes: a blade disk rotatable about a rotation shaft extending in an up-down direction and a plurality of cutter blades mounted on the blade disk. The blade disk includes a plurality of blade mounting sections having corresponding ones of the cutter blades mounted thereon, and a circumferential high-rigidity section for increasing rigidity of the blade disk between the blade mounting sections. The blade mounting sections are located on, and spaced from each other along, an imaginary reference circle concentric with a rotation center of the blade disk, and the circumferential high-rigidity section is located in such a manner as to interconnect the plurality of blade mounting sections along the reference circle, the circumferential high-rigidity section being formed in a generally concave-convex configuration by being depressed and protruded in a facewise direction of the blade disk.
