A steam turbine equipment comprising a steam turbine, a steam flow channel for guiding steam to the steam turbine, and a branch flow channel which connects a portion of the steam flow channel and the steam turbine to each other, the steam turbine equipment further comprising a valve device comprising: a main steam valve that is provided on the steam flow channel, in such a manner to adjust an opening and closing state of the steam flow channel; a regulating valve that is provided on the steam flow channel, in such a manner to be connected to the main steam valve in series, wherein the regulating valve includes a first valve seat, which is exposed in the steam flow channel, and a first valve body, which is movable relatively to the first valve seat so that it can abut against or be separated from the first valve seat to adjust a flowing state in the steam flow channel; an overload valve that provided on the branch flow channel, wherein said portion is arranged between the main steam valve and the regulating valve, and wherein the overload valve includes a second valve seat, which is exposed in the branch flow channel, and a second valve body, which is movable relatively to the second valve seat so that it can abut against or be separated from the second valve seat to adjust a flowing state in the branch flow channel; and a driving unit that is configured to drive the first valve body and the second valve body as a common driving source of the first valve body and the second valve body, such that the first valve body and the second valve body are interlocked with each other; characterized in that the second valve body of the overload valve has a through-hole that penetrates the second valve body in a steam flowing direction; the through hole being open regardless of a state of the second valve body with respect to the second valve seat, such that a steam in the branch flow channel would flow toward a downstream side of the overload valve through the through-hole regardless of said state. a main steam valve that is provided on the steam flow channel, in such a manner to adjust an opening and closing state of the steam flow channel; a regulating valve that is provided on the steam flow channel, in such a manner to be connected to the main steam valve in series, wherein the regulating valve includes a first valve seat, which is exposed in the steam flow channel, and a first valve body, which is movable relatively to the first valve seat so that it can abut against or be separated from the first valve seat to adjust a flowing state in the steam flow channel; an overload valve that provided on the branch flow channel, wherein said portion is arranged between the main steam valve and the regulating valve, and wherein the overload valve includes a second valve seat, which is exposed in the branch flow channel, and a second valve body, which is movable relatively to the second valve seat so that it can abut against or be separated from the second valve seat to adjust a flowing state in the branch flow channel; and a driving unit that is configured to drive the first valve body and the second valve body as a common driving source of the first valve body and the second valve body, such that the first valve body and the second valve body are interlocked with each other; characterized in that the second valve body of the overload valve has a through-hole that penetrates the second valve body in a steam flowing direction; the through hole being open regardless of a state of the second valve body with respect to the second valve seat, such that a steam in the branch flow channel would flow toward a downstream side of the overload valve through the through-hole regardless of said state.