An accumulator comprising: an accumulator housing which is provided with an oil port connected to a pressure piping and is provided with a gas charging port; a stay which is arranged in an inner side of said oil port within said housing and is provided with a liquid port opening in an end surface portion in a leading end of a tubular portion (16a, 22a); and a bellows which is arranged within said housing, is provided with a bellows cap in a floating end and comparts a space within said housing into a gas chamber in which gas is charged and a liquid chamber which is communicated with said oil port, and a safety mechanism for a pressure reducing time which confines a part of the liquid in said liquid chamber on the basis of a hermetically seal between said bellows cap or a retained member retained to said bellows cap and an end surface portion of said stay in the case that the pressure of said liquid chamber is reduced in connection with the pressure reduction of said pressure piping; characterized in that said accumulator further comprises a safety mechanism for an emergency which releases an internal pressure of said housing to said oil port side so as to prevent said housing from being exploded by the internal pressure of the housing which comes to a higher pressure in an emergency, for example, occurrence of fire disaster, and wherein said safety mechanism for the emergency has a taper portion in a corner portion between the tubular portion (16a, 22a) and the end surface portion of said stay, said taper portion is buckled at its root position in the emergency, and in the case that said taper portion is buckled, a pressure releasing flow path is formed between said bellows cap or said retained member and said taper portion as well as said bellows cap or said retained member and said end surface portion come away. an accumulator housing which is provided with an oil port connected to a pressure piping and is provided with a gas charging port; a stay which is arranged in an inner side of said oil port within said housing and is provided with a liquid port opening in an end surface portion in a leading end of a tubular portion (16a, 22a); and a bellows which is arranged within said housing, is provided with a bellows cap in a floating end and comparts a space within said housing into a gas chamber in which gas is charged and a liquid chamber which is communicated with said oil port, and a safety mechanism for a pressure reducing time which confines a part of the liquid in said liquid chamber on the basis of a hermetically seal between said bellows cap or a retained member retained to said bellows cap and an end surface portion of said stay in the case that the pressure of said liquid chamber is reduced in connection with the pressure reduction of said pressure piping; characterized in that said accumulator further comprises a safety mechanism for an emergency which releases an internal pressure of said housing to said oil port side so as to prevent said housing from being exploded by the internal pressure of the housing which comes to a higher pressure in an emergency, for example, occurrence of fire disaster, and wherein said safety mechanism for the emergency has a taper portion in a corner portion between the tubular portion (16a, 22a) and the end surface portion of said stay, said taper portion is buckled at its root position in the emergency, and in the case that said taper portion is buckled, a pressure releasing flow path is formed between said bellows cap or said retained member and said taper portion as well as said bellows cap or said retained member and said end surface portion come away.