A plasma monitoring device includes a plasma supplier including a power supply, a reaction gas supply line, and an emission nozzle for emitting plasma, which is generated therein, toward an object; a camera unit for obtaining an image of the plasma emission state; and a controller for obtaining a measurement value by converting pixel information of the image into a numerical value and comparing it with a reference value, which is a measurement value in a normal emission state, to check the plasma emission state. The camera unit obtains an image of the plasma emission state, and the controller analyzes the image to obtain a measurement value, which is used to monitor the state of plasma in real time and control the amount of reaction gas supplied to the plasma supplier and the plasma discharge condition, so that plasma is evenly emitted from the plasma supplier.