PURPOSE: To obtain a reflecting mirror of a parabolic antenna of a long service life by superposing a reinforcing net, and next, a reticulated reflecting member on the forming surface side of a die, and filling and forming a synthetic resin in which fibers are mixed.

CONSTITUTION: A reinforcing net 41 of a glass fiber, a reflecting member 8, and a forming material 42 are superposed on the forming surface 32. The material 42 consists of approximately 47% CaCO3, 32% polyester resin, and 21% glass fiber. When the upper die 35 provided with a nut 43 in a forming part 38 is allowed to descend to the lower die 31, allowed to further descend by fitting a bar 40 into a hole 34, and pressed by prescribed pressure, a reflecting mirror is obtained between the forming surface 32 and 36. During this time, the material 42 expands, while drawing the reflecting member 8 and the reinforcing net 41 to the periphery of the forming surface 32, the reflecting member approaches the front of the reflecting mirror, embedded without creases, the reflecting mirror having a satisfactory electric characteristic is obtained, and a service life of the reflecting member 8 is also extended.