PURPOSE: To precisely measure the electromagnetic shield effect of a ceiling by providing an umbrella in a freely opening/closing way to an antenna main body, providing an electromagnetic wave absorbing body to a rear side of the umbrella and an electromagnetic wave reflecting body to the front side.

CONSTITUTION: An umbrella 4 is provided to an antenna main body A in a freely opening/ closing way, an electromagnetic wave absorbing body 6 is provided to a rear side of the umbrella at the side of the antenna main body and an electromagnetic wave reflecting body 5 is provided to a front side of the umbrella 4. Then in the measurement of the electromagnetic wave shield effect of the ceiling, the umbrella 4 is spread to form the electromagnetic wave absorbing body 6 on the rear side of the umbrella and the electromagnetic wave reflecting body 5 on the front side of the umbrella respectively, an electromagnetic wave sent from other antenna is received by an antenna main body A and the electromagnetic wave passing through the antenna main body A is absorbed by the electromagnetic wave absorbing body 6 of the umbrella 4. Moreover, the electromagnetic wave reflected in the floor is reflected in the electromagnetic wave reflecting body 5 of the umbrella 4. Moreover, in the case of using the antenna for the transmission, the effect of the reflecting wave from the floor face is avoided. Furthermore, the electromagnetic wave reflecting body 5 is devised to receive the effect of an external incoming wave.