An error detection system for detecting an error in a cooling apparatus mounted in a power converter that drives, for example, a motor, the error detection system comprising: a first temperature sensor that measures a representative temperature (Tb) of the cooling apparatus, a second temperature sensor that measures an ambient air temperature (Ta), and a current sensor that measures an input/output current (Im) controlled by the power converter; wherein the error detection system is configured to: record measured signals sent from the first temperature sensor, the second temperature sensor, and the current sensor, respectively, as time-series data, extract from the recorded time-series data a data set, an extraction start time beginning the data of the data set being a time at which a difference between a measured temperature by the first temperature sensor and a measured temperature by the second temperature sensor is smaller than a minimum temperature difference (DT (min)), and also at which an input/output current value measured by the current sensor is greater than a minimum current value (Im(min)) and an extraction end time ending the data of the data set being a time at which the input/output current value measured by the current sensor is smaller than the minimum current value (Im(min)), and also at which the difference between the measured temperature by the first temperature sensor and the measured temperature by the second temperature sensor is smaller than the minimum temperature difference (DT(min)), calculate a thermal resistance of the cooling apparatus, on the basis of the extracted data set, detect an error in the cooling apparatus when the calculated thermal resistance reaches a planned inspection value. a first temperature sensor that measures a representative temperature (Tb) of the cooling apparatus, a second temperature sensor that measures an ambient air temperature (Ta), and a current sensor that measures an input/output current (Im) controlled by the power converter; wherein the error detection system is configured to: record measured signals sent from the first temperature sensor, the second temperature sensor, and the current sensor, respectively, as time-series data, extract from the recorded time-series data a data set, an extraction start time beginning the data of the data set being a time at which a difference between a measured temperature by the first temperature sensor and a measured temperature by the second temperature sensor is smaller than a minimum temperature difference (DT (min)), and also at which an input/output current value measured by the current sensor is greater than a minimum current value (Im(min)) and an extraction end time ending the data of the data set being a time at which the input/output current value measured by the current sensor is smaller than the minimum current value (Im(min)), and also at which the difference between the measured temperature by the first temperature sensor and the measured temperature by the second temperature sensor is smaller than the minimum temperature difference (DT(min)), calculate a thermal resistance of the cooling apparatus, on the basis of the extracted data set, detect an error in the cooling apparatus when the calculated thermal resistance reaches a planned inspection value. record measured signals sent from the first temperature sensor, the second temperature sensor, and the current sensor, respectively, as time-series data, extract from the recorded time-series data a data set, an extraction start time beginning the data of the data set being a time at which a difference between a measured temperature by the first temperature sensor and a measured temperature by the second temperature sensor is smaller than a minimum temperature difference (DT (min)), and also at which an input/output current value measured by the current sensor is greater than a minimum current value (Im(min)) and an extraction end time ending the data of the data set being a time at which the input/output current value measured by the current sensor is smaller than the minimum current value (Im(min)), and also at which the difference between the measured temperature by the first temperature sensor and the measured temperature by the second temperature sensor is smaller than the minimum temperature difference (DT(min)), calculate a thermal resistance of the cooling apparatus, on the basis of the extracted data set, detect an error in the cooling apparatus when the calculated thermal resistance reaches a planned inspection value.