Provided is a steam turbine driving machine, in which two shafts can be provided without increasing the space required for installing the machine, and in which two output shafts can be driven separately by a simple constitution. A steam turbine driving machine (1A) comprising an ahead high-pressure turbine (7) which can be driven upon the supply of steam, a first drive shaft (4) which can be driven by the ahead high-pressure turbine (7), an ahead first low-pressure turbine (11) and an ahead second low-pressure turbine (13) both of which can be driven upon the supply of steam discharged from the ahead high-pressure turbine (7), and a second drive shaft (14) which can be driven by the ahead first low-pressure turbine (11) and the ahead second low-pressure turbine (13), wherein the machine (1A) additionally comprises a steam dump pipe (33) and a vacuum valve (35); both of which can control the pressure of steam that is discharged from the ahead high-pressure turbine (7) and is supplied to the ahead first low-pressure turbine (11) and the ahead second low-pressure turbine (13).