PROBLEM TO BE SOLVED: To provide a grass-mowing blade capable of suppressing the damage of an installation, and a grass mower.SOLUTION: At the center of a grass-mowing blade 1, there is formed a connecting portion 11 to be connected to a grass mower 3, and the connecting portion 11 is surrounded with a circumferential portion 21 extending from the center of the connecting portion 11. The circumferential portion 21 is so wholly curved that the outer edge is sloped downward. The angle of inclination to a face B normal to a rotation axis A of the grass-mowing blade 1 becomes gradually larger toward the lower side. In the circumferential portion 21, there are formed notches 23 opened in the outer edge. If the distance from the rotation axis A to the outer edge of the circumferential portion 21 of a first end portion 27 is L1, the distance to the outer edge of a second end portion 29 is L2, and the distance to a predetermined position having no notch 23 is L3, L3>L1>L2 is satisfied.
