A depressurizing device includes a valve base, a first valve, a flexible member, and a top cover. The valve base has a pressure chamber and an outgassing chamber. Top and bottom surfaces of the pressure chamber have an opening and a first valve port respectively. The first valve is located in the pressure chamber and covers the first valve port. The flexible member is disposed on the valve base and has a depressurizing valve and a first outgassing port, the depressurizing valve covers the opening, and the first outgassing port is communicated with the outgassing chamber. A first outgassing channel is at least formed on the flexible member and communicates the pressure chamber to the outside of the valve base. The top cover is disposed on the flexible member and has a first depressurizing port and a second outgassing port.