A temperature detecting device for a power conversion device is provided in which the number of components can be reduced. An exemplary embodiment of the temperature detecting device includes: a plurality of temperature detecting elements that are provided in correspondence with a plurality of temperature detection objects, each temperature detecting element outputting a signal having a correlation with the temperature of the temperature detection object by being supplied power by a common power source; and a temperature detector that detects the temperatures of the temperature detection objects based on the signals having correlation with the temperatures of the temperature detection objects outputted from the temperature detecting elements. The temperature detector detects an average temperature of at least two temperature detection objects among the plurality of temperature detection objects or respective temperatures of the plurality of temperature detection objects based on the output signals.