A propulsion device for a ship, comprising: a rear propeller fixed to a rotation shaft; a front propeller that is rotatably supported on the rotation shaft in the front of the rear propeller; at least one bearing (13, 14, 15, 81, 82, 83) interposed in at least one of spaces between a hub of the front propeller and the rotation shaft and between the rotation shaft and a ship body; and an inverse rotation unit that inverts rotation of the rotation shaft, transfers the inverted rotation to the front propeller and comprises a gearbox that is accommodated in an installation space formed in a tail of the ship body in a state in which a plurality of gears for implementing inversion of the front propeller are embedded, wherein at least one measurement unit for measuring operating states of the at least one bearing (13, 14, 15, 81, 82, 83) is mounted to the rotation shaft, wherein the at least one bearing comprises: first and second thrust bearings that support thrust loads applied to the rotation shaft from the front propeller; a first radial bearing that supports a radial load applied to the rotation shaft from the front propeller; a second radial bearing that is respectively installed between the rotation shaft and the ship body and supports the rotation shaft in the front of the gearbox; and at least one of third and fourth thrust bearings that transfer axial forces transferred from the front propeller and the rear propeller to the rotation shaft toward the ship body characterized in that the propulsion device further comprising a generator unit that comprises coils and a magnetic substance installed between the hub of the front propeller and the rotation shaft so as to face each other and that generates electric energy due to opposite rotation of the coils and the magnetic substance when the rotation shaft rotates, wherein the electric energy is supplied as an energy source of the measurement unit. a rear propeller fixed to a rotation shaft; a front propeller that is rotatably supported on the rotation shaft in the front of the rear propeller; at least one bearing (13, 14, 15, 81, 82, 83) interposed in at least one of spaces between a hub of the front propeller and the rotation shaft and between the rotation shaft and a ship body; and an inverse rotation unit that inverts rotation of the rotation shaft, transfers the inverted rotation to the front propeller and comprises a gearbox that is accommodated in an installation space formed in a tail of the ship body in a state in which a plurality of gears for implementing inversion of the front propeller are embedded, wherein at least one measurement unit for measuring operating states of the at least one bearing (13, 14, 15, 81, 82, 83) is mounted to the rotation shaft, wherein the at least one bearing comprises: first and second thrust bearings that support thrust loads applied to the rotation shaft from the front propeller; a first radial bearing that supports a radial load applied to the rotation shaft from the front propeller; a second radial bearing that is respectively installed between the rotation shaft and the ship body and supports the rotation shaft in the front of the gearbox; and at least one of third and fourth thrust bearings that transfer axial forces transferred from the front propeller and the rear propeller to the rotation shaft toward the ship body first and second thrust bearings that support thrust loads applied to the rotation shaft from the front propeller; a first radial bearing that supports a radial load applied to the rotation shaft from the front propeller; a second radial bearing that is respectively installed between the rotation shaft and the ship body and supports the rotation shaft in the front of the gearbox; and at least one of third and fourth thrust bearings that transfer axial forces transferred from the front propeller and the rear propeller to the rotation shaft toward the ship body characterized in that the propulsion device further comprising a generator unit that comprises coils and a magnetic substance installed between the hub of the front propeller and the rotation shaft so as to face each other and that generates electric energy due to opposite rotation of the coils and the magnetic substance when the rotation shaft rotates, wherein the electric energy is supplied as an energy source of the measurement unit.