The present invention relates to a mower blade comprising: an assembly part having a connection hole a first blade part extended from an upper region on the right surface part of the assembly part, and having an upper surface, which is composed of a first processing part, formed to be horizontal to the upper surface part, which is also horizontal, of the assembly part, and having a lower surface, which is opposite the upper surface, formed to gradually move farther away from the upper surface while moving in the outward direction a second blade part extended from a lower region on the left surface part of the assembly part, and having a lower surface, which is composed of a second processing part, formed to be horizontal to the lower surface part, which is also horizontal, of the assembly part, and having an upper surface, which is opposite the lower surface, formed to gradually move farther away from the lower surface while moving toward the outer surface a first auxiliary blade part formed to protrude on a downwardly inclined cut surface, which is opposite a third processing part facing the first blade part on the upper surface part of the assembly part, having a fifth processing part provided on one side surface so as to be horizontal to the left surface part of the assembly part, and formed to be bent toward the connection hole and a second auxiliary blade part formed to protrude on an upwardly inclined cut surface, which is opposite a fourth processing part facing the second blade part on the lower surface part of the assembly part, having a sixth processing part provided on one side surface so as to be horizontal to the right surface part of the assembly part, and formed to be bent toward the connection hole. The present invention preemptively cuts, through a support blade part provided to the mower blade, grass becoming intertwined in between a gear case and blades or around the gear case, thereby increasing work efficiency, reducing working hours and further
