PURPOSE: To prevent a crack in a backing layer or peeling of resin from a fiber mat, by a method wherein the title deaerator is provided with a vacuum pad clogging the top of a mold, a cylinder for ascent and descent fitted to the vacuum cylinder, an air suction port and a vacuum pump connected with the air suction port.

CONSTITUTION: Two vacuum pads 12 are arranged on the top of a mold 4 and a cylinder 13 for ascent and descent is fitted to the top of the vacuum pad 12, in a deaerator 11. The cylinder 13 for the ascent and descent is fitted to a top plate 15 and a drop prevention cover 16 covering each of the vacuum pads 12 from the lower part is fitted to the top plate 15. A large number of tapered holes 10 forming a skid of a mat are bored in the mold 4. When resin 5 is applied onto the mold 4, the vacuum pad 12 of the deaerator 11 is lowered by the cylinder 13 for the ascent and descent and sucks a fitting frame 18 of the mold 4 by abutting against it. The inside of the vacuum pad 12 is deaerated and air bubbles between the mold 4 and resin 5 are removed by a vacuum pump 22 connected with the vacuum pad 12 and the inside of the tapered small hole 10 also provided on the mold 4 is filled with the resin 5.