A supercharging system, comprising: a first supercharger including a first compressor for compressing air to be supplied to an engine and a motor for driving the first compressor; a leakage current measuring part for measuring a leakage current of the motor; and a first controller for controlling the first supercharger, wherein the first controller includes a motor control part configured to, if a measurement result by the leakage current measuring part is not less than a first threshold, set an upper limit value of an output command value for the motor to be lower than when the measurement result is less than the first threshold, and to control an output of the motor within a range which does not exceed the upper limit value, wherein the first supercharger further includes: a first turbine configured to be capable of being rotary driven by exhaust gas from the engine and by the motor; and a first nozzle vane configured to adjust a flow path area of the exhaust gas flowing into the first turbine, wherein the first controller further includes a first vane control part for controlling an opening degree of the first nozzle vane on the basis of a measurement result of the leakage current measuring part, and wherein the first vane control part is configured to, if the measurement result by the leakage current measuring part is not less than the first threshold, control an opening degree of the first nozzle vane so as to reduce the flow path area compared to when the measurement result is less than the first threshold, in response to reduction of the upper limit value of the output command value for the motor by the motor control part. a first supercharger including a first compressor for compressing air to be supplied to an engine and a motor for driving the first compressor; a leakage current measuring part for measuring a leakage current of the motor; and a first controller for controlling the first supercharger, wherein the first controller includes a motor control part configured to, if a measurement result by the leakage current measuring part is not less than a first threshold, set an upper limit value of an output command value for the motor to be lower than when the measurement result is less than the first threshold, and to control an output of the motor within a range which does not exceed the upper limit value, wherein the first supercharger further includes: a first turbine configured to be capable of being rotary driven by exhaust gas from the engine and by the motor; and a first nozzle vane configured to adjust a flow path area of the exhaust gas flowing into the first turbine, wherein the first controller further includes a first vane control part for controlling an opening degree of the first nozzle vane on the basis of a measurement result of the leakage current measuring part, and wherein the first vane control part is configured to, if the measurement result by the leakage current measuring part is not less than the first threshold, control an opening degree of the first nozzle vane so as to reduce the flow path area compared to when the measurement result is less than the first threshold, in response to reduction of the upper limit value of the output command value for the motor by the motor control part. a first turbine configured to be capable of being rotary driven by exhaust gas from the engine and by the motor; and a first nozzle vane configured to adjust a flow path area of the exhaust gas flowing into the first turbine, wherein the first controller further includes a first vane control part for controlling an opening degree of the first nozzle vane on the basis of a measurement result of the leakage current measuring part, and wherein the first vane control part is configured to, if the measurement result by the leakage current measuring part is not less than the first threshold, control an opening degree of the first nozzle vane so as to reduce the flow path area compared to when the measurement result is less than the first threshold, in response to reduction of the upper limit value of the output command value for the motor by the motor control part.