A measurement system including an imaging device and a plasma processing device having a plasma generator configured to generate plasma from a gas supplied into a processing chamber and a controller. The imaging device is configured to generate optical information of the plasma from image data of imaged plasma in the processing chamber, and the controller is configured to convert the generated optical information of the plasma into a plasma parameter that determines physical characteristics of the plasma with reference to a storage that stores correlation information between the optical information of the plasma and measurement results of the plasma parameter.