To provide optimum picture display to an operator by adding a plant operation state also in the case of recognizing user's voice and displaying plant monitoring information.

The plant monitoring device is provided with a data processing part 3 for storing plant operation information and processing the stored information as monitoring information, a display part 4 for displaying the plant monitoring information processed by the data processing part 3 and a voice recognition part 2 for recognizing a voice and sending the recognized voice to the data processing part 3 as recognition data. In the case of displaying the plant monitoring information corresponding to the voice, an optimum monitoring picture corresponding to the plant operation state is provided to the operator.