To cause a safety mechanism for an emergency to be activated at lower pressure in comparison with a rupture plate, an accumulator comprises an accumulator housing, a stay having a liquid passage provided in the end surface portion on an end of a stepped tubular portion of the stay, a bellows with a bellows cap, a safety mechanism for pressure drop, and a safety mechanism for an emergency which is structured such that, in an emergency such as a fire, the bellows cap or a member held by the bellows cap presses the stay by high pressure due to the fire in the housing, to buckle the stay at a step of the stepped tubular portion, and open a liquid chamber, wherein a thin portion is provided circumferentially partially at the step of the stay to readily incline the end surface portion of the stay when the stay is buckled.