An exhaust turbine power generating system includes an internal combustion engine, an exhaust turbine power generator configured to perform electric power generation by rotating a turbine by using exhaust gas from the internal combustion engine, and an electronic control unit. The electronic control unit is configured to perform electric power generation control in which the exhaust turbine power generator is caused to perform electric power generation by controlling the exhaust turbine power generator and the electronic control unit is configured to perform powering control in which the exhaust turbine power generator is caused to perform powering such that the turbine is rotated by controlling the exhaust turbine power generator until a predetermined termination condition is satisfied after the internal combustion engine is started.