An accumulator vessel comprising a cylinder portion , both end portions of the cylinder portion being tightly closed, at least one of the end portions of the cylinder portion configuring an openable and closable end portion, the openable and closable end portion being configured to be closed tightly and to be opened and closed, the accumulator vessel comprising: a female thread formed on an inner circumferential surface of the openable and closable end portion; a screwable portion comprising, on an outer circumferential surface thereof, a male thread screwable into the female thread ; and a lid portion positioned at an axially inner side of the screwable portion , an axially inner surface of the lid portion configuring a pressure bearing plane, wherein the lid portion comprises an extending portion extending axially outward on an inner circumferential side, a large diameter portion following an inner circumferential surface of the openable and closable end portion; and a protruding portion , as the extending portion , positioned radially inward than an outer circumferential surface of the large diameter portion and protruding axially outward of the large diameter portion , characterized in that the extending portion is configured to abut against an axially inner end side of the screwable portion on an inner circumferential side thereof to separate an axially inner surface of the screwable portion on an outer circumferential side thereof apart from an axially outer surface of the lid portion on an outer circumferential side thereof, wherein the screwable portion comprises a recessed portion into which the protruding portion fits, the recessed portion having a depth allowing the axially inner surface of the screwable portion to be spaced apart from an axially outer surface of the large diameter portion of the lid portion to provide a gap therebetween with an axially outer surface of the protruding portion kept in abutment with a bottom surface of the recessed portion . a female thread formed on an inner circumferential surface of the openable and closable end portion; a screwable portion comprising, on an outer circumferential surface thereof, a male thread screwable into the female thread ; and a lid portion positioned at an axially inner side of the screwable portion , an axially inner surface of the lid portion configuring a pressure bearing plane, wherein the lid portion comprises an extending portion extending axially outward on an inner circumferential side, a large diameter portion following an inner circumferential surface of the openable and closable end portion; and a protruding portion , as the extending portion , positioned radially inward than an outer circumferential surface of the large diameter portion and protruding axially outward of the large diameter portion , characterized in that the extending portion is configured to abut against an axially inner end side of the screwable portion on an inner circumferential side thereof to separate an axially inner surface of the screwable portion on an outer circumferential side thereof apart from an axially outer surface of the lid portion on an outer circumferential side thereof, wherein the screwable portion comprises a recessed portion into which the protruding portion fits, the recessed portion having a depth allowing the axially inner surface of the screwable portion to be spaced apart from an axially outer surface of the large diameter portion of the lid portion to provide a gap therebetween with an axially outer surface of the protruding portion kept in abutment with a bottom surface of the recessed portion . <EOS>