A lawn mower (10) includes a driving source mounting portion (12) formed in a traveling frame (11), a driving source (13) mounted in the driving source mounting portion, and a lawn mowing unit (14) attached to the driving source. The lawn mowing unit is positioned below the traveling frame. A lower end (12b) of the driving source mounting portion and a lower end of the driving source are exposed from a bottom surface (17a) of the traveling frame. This bottom surface includes a frame-side seal surface (51) surrounding the lower end of the driving source mounting portion, and a lawn mowing unit peripheral surface (56) surrounding the frame-side seal surface. A waterproof member (70) is in tight contact with the frame-side seal surface, and waterproofs a portion between the bottom surface and driving source. When the lawn mower is viewed from below, the lawn mowing unit peripheral surface is formed over a range (Ar) from an outer circumferential edge (51b) of the frame-side seal surface to an outer circumferential edge (14a) of the lawn mowing unit. An inner circumferential edge (56a) of the lawn mowing unit peripheral surface is positioned higher than the outer circumferential edge of the frame-side seal surface. A boundary (57) between the frame-side seal surface and lawn mowing unit peripheral surface is formed into the shape of a step.
