A magnetron for a microwave oven is provided that decreases noise in an ISM band by minimizing a size of a lower end shield, and thus, minimizing EMI generation. In the magnetron for the microwave oven, as a midpoint of a side lead hole is positioned inside a virtual circle formed by points positioned at a predetermined distance from a midpoint of the shield disc and a side lead is connected in a straight line, there are advantages that a further bending process is not generated and a defective rate that occurs in the manufacturing process of the shield disc may be decreased.