PURPOSE: To make it possible to shorten the period of delivery and improve manufacturing efficiency by using a different material member for a shielding material which is divided into several sections in the peripheral direction of a cathode tube or the like, and interconnecting the edges of these shielding materials with a joint so that they may be shaped into cylindrical shape.

CONSTITUTION: Permalloy is used for shielding members 11, 12, 13, and 14, which are made of plate cut out into specified shape respectively. The shielding members 11 and 13 are identical to each other in shape while the shielding members 12 and 14 are identical to each other in shape. They are connected with a joint 15 so that they may be formed in square pipe and fitted into an electromagnetic shielding unit 16.