To provide a simple shielding device at a low cost, which can be easily retrofitted to an existing cabinet.

In retrofitting the shielding device, guide rails 30, 30 are mounted on side plates 11, 11 of a cabinet main body 10 along a front opening section 10a thereof, and a hanger rod 41 attached to an upper edge of a shielding sheet 40 is hooked on engaging grooves 32 formed in upper edges of the guide rails 30, 30, respectively, followed by locking a lower edge of the shielding sheet 40 by a locking means 50, to thereby cover the front opening section 10a of the cabinet main body 10.