An explosion-proof decompression plate is provided outside the explosion-proof window of an architecture or equipment. A convex part that protrudes out of the window is formed in the center of the decompression plate, and a flange is formed around the convex part. Further, a confined space is formed inside the decompression plate that is opposite to the convex part. Several thru holes are formed on the flange, and a lock-joint portion of which the area is smaller than the thru hole is formed. Several joint ribs easily splitting are formed between the flange and the lock-joint portions to connect. Accordingly, when the air blast occurs in the architecture or equipment, the decompression plate is thrust away by the blast pressure caused by the air blast and an open mouth is formed to vent out the blast pressure.