The invention relates to equipment, belongs to the technical field of machining of metal rods, in particular to a metal rod cutting device and a cutting method of a metal rod. The metal rod cutting device comprises a cutting platform, wherein a cutter is mounted on the cutting platform; a plurality of roller shafts are mounted on the left side of the cutting platform; a first metal rod is arrangedon the roller shaft and can be moved rightwards; multiple groups of roller wheels are mounted on the left side of the cutting platform; each group of roller wheel at least comprises a front roller wheel and a rear roller wheel; the groups of roller wheels are also connected with an electromotor; a lifting air cylinder is mounted under each group of roller wheel; a corresponding part, which contacts a first metal rod, called as a contact point, is arranged between each of the front roller wheels and each of the rear roller wheels; when the air cylinders descend, the corresponding contact point, arranged between the each of the front roller wheels and each of the rear roller wheels, is separated from the corresponding first metal rod arranged on the corresponding roller shaft; and when theair cylinders ascend, the corresponding contact point, arranged between the each of the front roller wheels and each of the rear roller wheels, supports the corresponding first metal rod; and therefore, the metal rod cutting device and the cutting method of the metal rod disclosed by the invention have the advantages of being easy in cutting, reduced in consumption of saw blades of a cutting machine, and flat in end faces of second metal rods.