The present invention relates to an apparatus to cut a stem of agricultural crops, which has improved stem (vine) cutting ability when the stem of agricultural crops is lifted and cut by a cutting blade installed in a cutting rotary shaft while cutting the step (vine) of agricultural crops, such as potato having stems, cucumber, watermelon having a vein, and the like. According to the present invention, the apparatus to cut a stem of agricultural crops comprises: the cutting rotary shaft detachably mounted on a powered agricultural machine, such as a tractor, and including a plurality of hinge-coupled cutting blades, which receive power withdrawn from the powered agricultural machine to be rotated so as to cut the stem and the vein of agricultural crops； and a plurality of step lifting guide blades to guide the stem and the vein of agricultural crops. The cutting blades installed in the cutting rotary shaft are formed with a pair of first and second unit cutting blades, and have a caret shape having the bottom portion with both opened sides. The cutting blades comprises: a central cutting blade including a pair of unit cutting blades with an equal length formed in a center with respect to each stem lifting guide blade； an inner cutting blade with a length identical with or similar to that of the unit cutting blade of the central cutting blade formed at a position separated from the center to both sides of the stem lifting guide blade； and a side cutting blade formed with an outer unit cutting blade with a length greater than that of the inner unit cutting blade.본 발명은 고구마와 같이 줄기를 가지는 농작물 또는 오이, 수박 등과 같은 넝쿨 농작물 등의 농작물 줄기(넝쿨)를 절단하되, 농작물 줄기를 상승시켜 절단용 회전축에 구비된 절단날로 절단함에 있어 줄기(넝쿨)의 절단능력을 향상시킬 수 있도록 이루어진 농작물 줄기 절단장치이다.이러한 본 발명인 농작물 줄기 절단장치는 트랙터와 같은 동력농기계에 장착 및 탈착이 가능하고, 동력농기계로부터 인출되는 동력을 전달받아 회전하여 농작물 줄기 및 넝쿨을 절단하도록 하는 힌지결합되는 다수의 절단날이 구비된 절단용 회전축과, 농작물 줄기 및 넝쿨을 안내하는 다수의 줄기상승용 안내날을 포함하는 농작물 줄기 절단장치에 있어서, 상기 절단용 회전축에 구비되는 다수의 절단날은 제1 단위 절단날, 제2 단위 절단날이 한쌍으로 이루어지며, 하단부분이 양측이
