A stiffened diaphragm manufacturing method and the manufactured diaphragm using same are provided. The manufacturing method includes the steps of: applying a hot glue layer to a side of a stiffened plate; putting a base layer on the hot glue layer, and then heating and adhering the base layer and the stiffened plate together; and performing a pressing process on the base layer and the stiffened plate to form a diaphragm having a central portion and a surround portion. The stiffened plate is coated uniformly with the hot glue layer and then put on the base layer to undergo heating and adhesion; hence, an oversupply or undersupply of a glue will be unlikely to happen. Furthermore, the manufacturing process is simple and attains high-strength adhesion between the stiffened plate and the base layer.