To provide a device for supplying a lubricating oil into a steam tur bine, which can maintain a negative pressure condition in a bearing chamber even through a manhole of a tank is opened during operation of the turbine, so as to prevent the lubrication oil from leaking through an oil slinger seal.

A device for supplying a lubricating oil into a steam turbine, comprises a bearing chamber 60, a first oil tank 11 having a booster pump 13, and a second oil tank 12, the bearing chamber 60 being connected with the booster pump 13 through an oil supply pipe 17, and the bearing chamber 60 being connected with the second oil tank 12 through an oil return pipe 18. Further, the lower part of the first oil tank 11 and the lower part of the second oil tank 12 are connected with each other through an oil communicating pipe 20, and the upper part of the first oil tank and the upper part of the second oil tank are connected with each other through a gas communication pipe 25 which is provided therein with a gas flow control valve 26.